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International Journal of Neuropsychopharmacology

Oxford University Press (OUP)

Preprints posted in the last 90 days, ranked by how well they match International Journal of Neuropsychopharmacology's content profile, based on 14 papers previously published here. The average preprint has a 0.01% match score for this journal, so anything above that is already an above-average fit.

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Acute inflammation-mediated attenuation of behavioural sensitization in methamphetamine-sensitized mice via distinct COX-2 and TNF-α pathways

Shinohara, R. C.; Ishikawa, S.; Matsumoto, R.; Ito, K.; Tonosaki, M.; Matsuyama, S.; Ohgidani, M.; Koga, M.; Hashimoto, N.; Kusumi, I.; Takahiro, K. A.

2026-05-12 pharmacology and toxicology 10.64898/2026.05.08.723429 medRxiv
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Background and PurposeWhile inflammation has been generally considered to exacerbate symptoms of schizophrenia, some clinical observations suggest that acute inflammation may alleviate positive symptoms. However, animal models often use excessive inflammatory stimuli, and the effects of acute inflammation--comparable to levels observed in patients--remain unknown. Experimental ApproachTo address this, we examined whether acute inflammation induced under relatively mild, clinically relevant conditions suppresses behavioural sensitization in methamphetamine (METH)-sensitized mice, a model of psychostimulant-induced psychosis with relevance to certain aspects of positive symptoms of schizophrenia. We used a repeated METH (1 mg/kg) sensitized model to evaluate the effects of acute inflammation on behavioural sensitization. Acute inflammation was induced via two methods using either lipopolysaccharides (LPS; 1 g/kg) to mimic peripheral immune activation or restraint stress (RS; single 2-h exposure) to model the neuroinflammation induced by psychological stress. LPS doses were adjusted with reference to the magnitude of peripheral cytokine elevation reported in patients, and RS was applied in short single sessions to avoid excessive inflammation. Key ResultsBoth LPS and RS significantly suppressed behavioural sensitization, without inducing other behavioural abnormalities. This suppression was dependent on toll-like receptor-4 activation. LPS-mediated suppression involved cyclooxygenase-2, whereas RS-mediated suppression was linked to the microglia-derived tumour necrosis factor-. LPS did not alter, whereas RS significantly reduced the striatal extracellular dopamine levels. Conclusion and ImplicationsThese findings suggest that acute inflammation suppresses behavioural sensitization through distinct mechanisms depending on the inflammatory trigger, providing a framework for understanding how inflammation may influence psychosis-related processes, with potential relevance to schizophrenia.

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Acute ketamine treatment produces long-term anxiolytic effects despite increasing oxidative stress in female Wistar Kyoto rats

Lemeshova, A.; Abdirahaman, F.; Haidari, H.; Zhao, C.; Limbada, A.; Honeycutt, J. A.

2026-07-01 neuroscience 10.64898/2026.06.26.734907 medRxiv
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Treatment-resistant depression and anxiety remain major challenges in psychiatry, particularly in female patients, who are disproportionately affected yet remain underrepresented in preclinical ketamine research. The present study investigated short- and long-term anxiolytic effects of acute subanesthetic ketamine administration in female Wistar-Kyoto (WKY) rats, a validated genetic model of treatment-resistant affective dysfunction. Subjects received a single intraperitoneal injection of saline vehicle or racemic ketamine (5, 10, or 15 mg/kg), followed by acoustic startle response (ASR) testing 24 hours and 7 days later. Oxidative stress was assessed using 8-oxo-2'-deoxyguanosine (8-oxo-dG) immunofluorescence in the basolateral amygdala (BLA), prefrontal cortex (PFC), and hippocampus, alongside analysis of parvalbumin-positive (PV+) interneurons. Ketamine treatment produced dose- and time-dependent behavioral effects with 10 mg/kg eliciting the strongest delayed anxiolytic-like response at 7 days, while 15 mg/kg showed more immediate behavioral effects at 24 hours. While ketamine did not alter PV+ cell count, it significantly increased oxidative stress markers globally in the BLA and prelimbic region of the PFC and specifically in the PV+ interneurons in the BLA. The findings suggest that ketamine's therapeutic effects in female WKY rats may involve region-specific modulation of stress circuitry and oxidative signaling rather than gross interneuron loss. Overall, the study provides evidence for sex-dependent and temporally dynamic effects of ketamine in a translational model of treatment-resistant anxiety and depression.

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Effects of NMDA antagonists on social behaviour: a systematic review and meta-analysis of preclinical studies

Gallas-Lopes, M.; Abreu, M. B.; Andrades, M.; Arbo, B. D.; Bastos, L. M.; Caetano, T. C.; Muller, D. V.; Patelli-Alves, A.; Rosa, D. A.; Stein, D. J.; Herrmann, A. P.

2026-05-15 pharmacology and toxicology 10.64898/2026.05.13.724847 medRxiv
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Social withdrawal is a key component of the negative symptom domain of schizophrenia, and pharmacological blockade of the N-methyl-D-aspartate receptor (NMDAR) is widely used to model schizophrenia-relevant phenotypes in animals. However, findings on social behaviour are inconsistent across paradigms and laboratories. We therefore conducted a systematic review and meta-analysis to synthesise the effects of dizocilpine, ketamine, and phencyclidine on social interaction and social preference, to evaluate whether clinically approved antipsychotics modify these outcomes, and to examine locomotor activity measured within the same social tests to aid interpretation. We searched Embase, PubMed and Web of Science without language or date restrictions. Controlled in vivo studies in laboratory animals administering an eligible NMDAR antagonist and reporting social interaction and/or social preference outcomes were included. Two reviewers independently screened records, extracted data and assessed risk of bias. Effect sizes were computed as standardised mean differences and synthesised using correlated multilevel random-effects models with cluster-robust variance estimation. In total, 264 studies met the inclusion criteria. Overall, NMDAR antagonists were associated with reduced social interaction and reduced social preference relative to controls, although the social preference literature appeared vulnerable to small-study effects and imprecision. Locomotor activity measured during social interaction tests tended to be higher following NMDAR antagonists, whereas during social preference no consistent overall change was observed. In animals exposed to NMDAR antagonists, antipsychotics increased social behaviour, but these changes commonly co-occurred with reduced locomotion during social interaction tests, suggesting that improvements in social measures may partly reflect altered behavioural competition and time allocation rather than selective restoration of social functioning. Taken together, the evidence supports an overall link between NMDAR antagonism and reduced social behaviour, but the strength and interpretability of this signal depend on the paradigm and are constrained by heterogeneity and limitations in reporting.

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Unexpected antidepressant-like effects of temozolomide in a mixed sex-cohort of adult rats: role of hippocampal FADD protein

Galvez-Melero, L.; Garcia-Fuster, M. J.

2026-04-27 pharmacology and toxicology 10.64898/2026.04.23.720315 medRxiv
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Temozolomide is the gold standard chemotherapeutic agent used in the treatment of glioblastoma multiforme. Yet its pharmacological use has been linked to the emergence of depressive- and/or anxiety-like behaviors, probably through the inhibition of hippocampal neurogenesis. Since prior studies reporting these negative effects were based on prolonged treatment paradigms (i.e., from 2 weeks to up to 6 months), and given the few reports that have included female rodents in their studies, our approach aimed at further characterizing the behavioral effects induced by temozolomide (25 mg/kg, 1 or 2 cycles, 5 days/cycle) in a mixed-sex cohort of adult rats. To do so, rats were scored across time through specific behavioral tests that capture diverse manifestations of affective-like responses (forced-swim, open field, novelty-suppressed feeding and sucrose preference) or cognitive performance (Barnes maze). At the neurochemical level, we ascertained the effects of 2 cycles of temozolomide on hippocampal neurogenesis (neural progenitors with NeuroD) and other potential neuroplasticity targets (i.e., FADD, BDNF). The main results showed that temozolomide induced unexpected antidepressant-like responses in a treatment-duration manner while decreased hippocampal FADD, a neuroplastic marker previously associated with the acute and repeated actions of most antidepressants. These results break the prior dogma linking increased hippocampal neurogenesis with antidepressant-like efficacy, and suggest that other mechanisms of action, such as the one described through the neuroplastic molecule FADD, might be responsible for the antidepressant-like actions of temozolomide, even in the presence of impaired neurogenesis. Our results, in conjunction with the prior data, suggested cycle- and/or length-dependent treatment effects in terms of temozolomides antidepressant- vs. depressant-like profile, while proposing a novel biomarker of its treatment response.

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PARP inhibition with 3-aminobenzimide attenuates behavioral, cardiovascular, and neuroinflammatory effects of chronic stress

Wills, L. J.; Wang-Heaton, H.; Polichnowski, A. J.; Thomas, K. L.; Jewett, B. E.; Jewett, S.; Aldridge, G.; Ordway, G. A.; Brown, R. W.; Chandley, M. J.

2026-05-01 neuroscience 10.64898/2026.04.28.721400 medRxiv
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BackgroundMajor depressive disorder (MDD) affects approximately 20% of the population, with over 30% of cases demonstrating treatment resistance. Postmortem analyses have revealed increased poly (ADP-ribose) polymerase 1 (PARP-1) expression in prefrontal cortical white matter of individuals with MDD, suggesting PARP-1 as a potential therapeutic target. Chronic stress, a major risk factor for depression, affects multiple physiological domains including behavior, cardiovascular function, neuroinflammation, and gut-brain axis signaling. MethodsWe conducted a comprehensive multi-system investigation of PARP inhibition effects on stress-induced pathophysiology using the social defeat stress/chronic unpredictable stress (SDS+CUS) rodent model. In the primary study, male Sprague-Dawley rats (N=32) underwent 10 days of SDS+CUS while receiving daily treatment with the PARP inhibitor 3-aminobenzamide (3-AB; 40mg/kg), selective serotonin reuptake inhibitor fluoxetine (FLX; 10mg/kg), or saline (0.9% NaCl), with non-stressed controls included. Behavioral outcomes were assessed via sucrose preference and social interaction tests. Neurobiological analyses examined PARP-1 expression, microglial morphology, and proinflammatory cytokine levels (IL-1{beta}, TNF-, IL-6) in relevant brain regions. In a parallel cardiovascular study, a separate cohort of stressed rats (N=8) received either saline or 3-AB treatment while hemodynamic parameters were monitored via telemetry before, during, and after stress exposure. Exploratory gut microbiome analyses were also conducted (see Supplemental Materials). ResultsSaline-treated stressed rats demonstrated significantly elevated anhedonia and social avoidance compared to all other groups, while 3-AB treatment prevented these behavioral deficits. Cardiovascular monitoring revealed that stressed saline-treated rats developed significant elevations in systolic and mean blood pressure with decreased heart rate compared to baseline, whereas 3-AB treatment prevented these hemodynamic changes. Neurobiological analyses showed that FLX-treated stressed rats unexpectedly exhibited elevated PARP-1 expression in prefrontal cortical gray matter. Microglial morphological analysis revealed significantly more prolate (activated) microglia in the saline-treated stressed rats compared to all other treatment groups. Saline-treated stressed rats exhibited significantly increased hippocampal proinflammatory cytokines, with 3-AB treatment specifically normalizing TNF- levels. ConclusionPARP inhibition with 3-AB provides multi-system protection against chronic stress effects, preventing behavioral deficits, cardiovascular dysfunction, and neuroinflammation. These findings establish PARP-1 as a key mediator in the systemic pathophysiology of chronic stress and highlight PARP inhibition as a promising therapeutic approach for stress-related disorders with treatment-resistant features. Significant OutcomesO_LIPARP inhibition with 3-aminobenzamide (3-AB) prevented stress-induced behavioral deficits (anhedonia and social avoidance) in a validated rodent model combining social defeat and chronic unpredictable stress. C_LIO_LI3-AB treatment prevented stress-induced increases in arterial blood pressure. C_LIO_LIPARP inhibition prevented microglial activation and reduced proinflammatory cytokine expression (IL-1{beta} and TNF-) in stress-sensitive brain regions, supporting an anti-neuroinflammatory mechanism of action. C_LIO_LIFLX-treated stressed rats unexpectedly showed elevated PARP-1 expression in prefrontal cortical gray matter, suggesting a previously unrecognized interaction between serotonergic antidepressants and PARP-1 signaling that warrants further investigation. C_LIO_LIThe multi-system protective effects of PARP inhibition, spanning behavioral, cardiovascular, and neuroinflammatory domains, suggest therapeutic potential for treatment-resistant depression. C_LI LimitationsO_LIThis study examined only male rats, limiting generalizability to female subjects despite the higher prevalence of MDD in women. C_LIO_LIBehavioral assessments were limited to anhedonia and social interaction; additional tests of other depression-relevant behaviors would provide a more comprehensive phenotypic profile. C_LIO_LILong-term effects of 3-AB treatment beyond the 10-day stress paradigm remain unexplored. C_LI

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The Effects of Cognitive Behavioral Therapy for Insomnia on Cardiovascular and Immunological Outcomes: A Randomized-Controlled Study

Reyt, M.; Jarrin, D. C.; Perrault, A. A.; Borgetto, F.; Smith, D.; Gong, K.; Tarelli, L.; Savard, J.; Dang-Vu, T. T.; Gouin, J. P.

2026-07-02 pharmacology and therapeutics 10.64898/2026.06.30.26356933 medRxiv
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Evidence suggests that insomnia disorder is associated with pathophysiological alterations that may contribute to long-term physical, mental and inflammatory-related health risks. Cognitive behavioral therapy for insomnia (CBTi) is the first-line treatment for insomnia disorder, yet its effects on physiological outcomes remain unclear. This randomized-controlled trial examined the effects of CBTi on cardiovascular and immunological biomarkers. Sixty-two participants with insomnia disorder were randomized to group-CBTi (N = 33, 75.8% female, Mage = 48.8 + 17.1 years) or Waitlist (WL) control (N = 29, 75.9% female, Mage = 52.2 + 15.6 years). Cardiovascular parameters included systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), and nocturnal heart rate variability (HRV). Inflammatory markers from blood samples included C-reactive protein (CRP), tumor necrosis factor-alpha (TNF- ), interleukin-6 (IL-6) and brain-derived neurotrophic factor (BDNF). All outcomes were assessed at baseline (T1), post-treatment assessment (T2, following completion of CBTi or WL period), and 6-months for the WL group (T3, after CBTi for the WL participants). No significant Group-by-time effects were observed for SBP, DBP, HR, HRV and any inflammatory markers (ps > .05) from T1 to T2. When pooling treatment effects following CBTi exposure across both groups (T1 to T2 in CBTi group and T1 to T3 in WL group), no significant biomarker changes were observed. Overall, results indicate that CBTi did not produce detectable changes in cardiovascular or inflammatory markers among healthy individuals with insomnia disorder. These findings suggest physiological responses to CBTi are complex and may reflect dynamic and context-dependent processes (https://www.isrctn.com/ISRCTN13983243).

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Preliminary Non-Randomized Clinical Trial of Subcutaneous Esketamine in Treatment-Resistant Depression: Exploring Adjunctive Effects of Ketamine-Assisted Psychotherapy

Varela, Y. M.; Ribeiro, P. C.; de Souza, G. M.; Falchi-Carvalho, M.; Barbalho, J. d. S. F.; Gomes, R. B. d. O.; Gurgel, M. M. M.; Pereira, B. C.; Souza, P. M. d. L.; Goncalves, K. T. d. C.; Muniz, M.; de Almeida, V. R. N.; Pereira, L. F. D.; Barbosa, D. C.; de Carvalho, B. S.; Lopes, E. I. T. C.; de Oliveira, A. C.; de Araujo, D. B.; Palhano-Fontes, F.; Fernandes-Osterhold, G.; Galvao-Coelho, N. L.

2026-06-02 psychiatry and clinical psychology 10.64898/2026.05.31.26354555 medRxiv
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Abstract Background Ketamine has emerged as an effective rapid-acting treatment for treatment-resistant depression (TRD), producing significant antidepressant effects within hours of administration. Given ketamine's capacity to induce states of heightened neuroplasticity and psychological openness, psychotherapy may represent a meaningful complement to its pharmacological effects - facilitating emotional processing, cognitive restructuring, and the consolidation of therapeutic gains. However, the adjunctive potential of structured psychotherapeutic support in ketamine-based interventions remains largely unexplored. Methods This preliminary, non-randomized, open-label clinical trial evaluated the adjunctive effects of ketamine-assisted psychotherapy (KAP) in an outpatient setting. Forty-six patients with TRD received eight weekly sessions of subcutaneous esketamine (0.5-1.0 mg/kg) and were allocated into two groups: esketamine without psychotherapeutic support (n = 23) and esketamine combined with structured KAP encompassing preparation, dosing accompaniment, and post-session integration (n = 23). Depressive symptoms were assessed using the Montgomery-Asberg Depression Rating Scale (MADRS) and the Beck Depression Inventory-II (BDI-II) at multiple timepoints during treatment and at follow-up assessments up to six months after protocol completion. Results Both groups showed significant reductions in depressive symptoms throughout treatment. The KAP group demonstrated greater clinical improvement by the end of treatment, with between-group differences on the MADRS emerging at sessions 7 and 8. MADRS response and remission rates were 52.2% and 34.8% in the KET group, and 78.3% and 78.3% in the KAP group, respectively. BDI-II scores indicated earlier subjective improvement in the KAP group, with between-group differences emerging as early as the second session and persisting across multiple timepoints. No significant between-group differences were observed during the six-month follow-up, with both groups maintaining symptom reductions comparable to end-of-treatment levels. Conclusions These findings suggest that structured psychotherapeutic support may be associated with early clinical response and remission rates in subcutaneous esketamine treatment for TRD, potentially through facilitation of emotional processing, psychological flexibility, and behavioural change. Further controlled studies are needed to clarify the specific contribution of psychotherapy, investigate the mechanisms underlying this interaction, and optimize integrated treatment approaches for TRD. The trial was registered at https://ensaiosclinicos.gov.br/rg/RBR-1072m6nv . Keywords: esketamine; treatment-resistant depression; ketamine-assisted psychotherapy; innovative therapies.

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Glucagon-like peptide-1 receptor agonist, semaglutide, attenuates intravenous self-administration of fentanyl in female rats

Rojas, K. E.; Gee, S. C.; Wernette, C. L.; Wang, E. X.; Nguyen, E. T.; Nguyen, J. D.

2026-05-21 pharmacology and toxicology 10.64898/2026.05.19.726324 medRxiv
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Current treatments for opioid use disorder (OUD) have major barriers to access. As such, researching new potential therapies for OUD is important to public health. Previous research has implicated glucagon-like peptide-1 (GLP-1) receptor agonists in decreasing the use of addictive substances by animals. In this study, female Wistar rats (N=32) were surgically implanted with jugular catheters and trained to self-administer fentanyl at a fixed-ratio 1 (FR1) schedule of reinforcement for 21 sessions under short- (ShA; 1 hour) or long-access (LgA; 8 hours) conditions. Next, the animals received injections of semaglutide (0.1 mg/kg, s.c.) or saline (0.9% NaCl, s.c.) prior to another FR1 session. The animals underwent a progressive ratio (PR) schedule of reinforcement while receiving saline (i.v.) or fentanyl (0.625-10 {micro}g/kg/inf, i.v.) and semaglutide (0.1 mg/kg, s.c.) or saline (s.c.). Next, the animals underwent a semaglutide (0-0.1 mg/kg, s.c.) dose response procedure at FR1 and a single dose of fentanyl (2.5 {micro}g/kg/inf, i.v.). Following drug discontinuation, spontaneous locomotor activity and withdrawal-like symptoms were measured. Semaglutide dose-dependently decreased fentanyl rewards under ShA and LgA conditions (p<0.05). Under a PR, semaglutide significantly decreased breakpoint (p<0.05), suggesting semaglutide decreases motivation to self-administer fentanyl. Semaglutide-treated ShA animals displayed significantly less withdrawal-like behavior (p<0.05) but not LgA animals. Overall, these findings suggest semaglutide may modulate motivation to seek opioid reward and could be useful in the development of pharmacotherapies to address OUD.

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Activation of mGlu2 receptors reverses persistent post-methamphetamine deficit in object-in-place recognition memory.

Galbava, V.; Wu, L.; Schwendt, M.

2026-05-28 neuroscience 10.64898/2026.05.25.727633 medRxiv
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Background/ObjectivesPersistent cognitive impairments are prevalent in methamphetamine (meth) use disorder and contribute to maladaptive decision-making and increased relapse vulnerability. There are currently no effective treatments for meth-associative cognitive deficits, and their neurobiological underpinnings remain incompletely understood. This study investigated the effects of chronic meth self-administration on episodic-like recognition memory and evaluated whether pharmacological potentiation of metabotropic glutamate receptor subtype 2 (mGlu2) could rescue these deficits. MethodsAdult male Sprague-Dawley rats underwent 7 days of limited- (1h/day) followed by 14 days of extended-access (6h/day) meth self-administration, followed by 30 days of abstinence. Recognition memory was assessed using the object-in-place (OIP) task. A positive allosteric modulator of mGlu2 receptors, LY-487379 (25 mg/kg, s.c.), was administered prior to the memory test. In parallel, changes in total and surface mGlu2/3 protein levels in the prelimbic and perirhinal cortices were evaluated. ResultsRats with extended access to meth self-administration exhibited escalated drug intake and persistent deficits in OIP memory. Administration of LY-487379 reversed this deficit. Total mGlu2/3 protein levels were unaltered; however, meth exposure was associated with a significant increase in surface mGlu2/3 receptor expression in both cortical regions examined. ConclusionsThese results demonstrate that chronic meth produces persistent cognitive dysfunction that can be rescued by mGlu2 receptor potentiation. The observed increase in surface mGlu2/3 expression may represent a compensatory response to chronic glutamatergic dysregulation, but it appears to be insufficient to restore cognitive function alone, without pharmacological enhancement. The current data encourage further exploration of mGlu2 role in stimulant-associated cognitive dysfunction. HighlightsChronic methamphetamine self-administration produced persistent deficits in episodic-like recognition memory in male rats and dysregulation of mGlu2/3 receptors in the prelimbic and perirhinal cortices. Systemic pharmacological potentiation of mGlu2 receptors rescued meth-associated memory deficits. mGlu2 receptor potentiation may represent a promising therapeutic strategy for treating stimulant-associated cognitive dysfunction. Increased surface mGlu2/3 expression may represent a compensatory adaptation to post-methamphetamine glutamatergic dysfunction, but it is not sufficient to restore cognition alone, without pharmacological enhancement.

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Chronic cocaine exposure negatively impacts Long-COVID-like outcomes produced by the SARS-CoV-2 spike protein in the rat

Davis, S. E.; Stern, D. R.; Inan, S.; Vu, E.; Lopez, D.; Anwuri, F.; Ghilotti, M. G.; Meissler, J. J.; Unterwald, E. M.

2026-06-02 neuroscience 10.64898/2026.06.02.729575 medRxiv
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Acute COVID-19 outcomes are exacerbated by substance use, however, the impact of substance use on Long-COVID is unknown. Here, we investigated the impact of chronic cocaine administration on spike-induced Long-COVID-like outcomes in the rat. Rats received intermittent chronic cocaine administration and a single intravenous injection of the SARS-CoV-2 spike protein. Two months following spike administration, Long-COVID-like outcomes were assessed. Exposure to spike protein in the presence of cocaine produced a persistent reduction in weight gain as compared with controls or spike protein alone. Further, cocaine-treated rats exposed to spike had lower withdrawal thresholds compared to control animals as well as their own baseline, suggesting increased pain sensitivity. Spike and/or cocaine increased the ratio of interleukin-6 (IL-6) to interleukin-10 (IL-10) levels in the hippocampus, indicating a shift towards a proinflammatory state. Paw withdrawal thresholds were positively correlated with IL-10 levels in the hippocampus and prefrontal cortex. Regarding olfaction, rats exposed to spike spent less time sniffing an odor attractant. Cocaine produced an anxiolytic-like phenotype during the elevated plus maze test. Further analysis of behaviors on the maze revealed that the latency to enter the open arms was shorter in rats exposed to spike or cocaine, suggesting a possible impulsive-like phenotype in these animals. These findings demonstrate the negative impact of cocaine on Long-COVID-like outcomes suggesting a need for increased clinical observations of people with co-occurring Long-COVID and cocaine use disorder. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=59 SRC="FIGDIR/small/729575v1_ufig1.gif" ALT="Figure 1"> View larger version (10K): org.highwire.dtl.DTLVardef@12fdc19org.highwire.dtl.DTLVardef@11b1b0dorg.highwire.dtl.DTLVardef@8d1e21org.highwire.dtl.DTLVardef@b53d20_HPS_FORMAT_FIGEXP M_FIG C_FIG

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A network meta-analysis of randomised controlled trials of antipsychotic medications to assess their comparative efficacy and tolerability in autistic people

Deb, S.; Limbu, B.; Lopez Lopez, J. A.; Roy, M.; Murugan, M.; Roy, A.; Brizard, B. A.; Santambrogio, J.

2026-05-14 pharmacology and therapeutics 10.64898/2026.05.11.26352928 medRxiv
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BackgroundA high proportion of autistic people receive off-license antipsychotic medication, often in the absence of a mental illness, primarily for behaviours that challenge, which is a public health concern. Although meta-analyses have been published recently, there is a lack of a comprehensive network meta-analysis to inform clinicians about the relative efficacy and safety of antipsychotic medications. AimsTo conduct a network meta-analysis of available RCTs of antipsychotic medications involving autistic participants to assess the relative efficacy of different antipsychotics and their adverse effects. MethodWe searched seven databases and hand-searched ten relevant journals. Two authors independently screened titles, abstracts, and full papers, extracted data, and assessed their quality. ResultsWe analysed data from 22 RCTs involving 1562 autistic people. The largest mean difference with 95% confidence interval in the Aberrant Behaviour Checklist-Irritability (ABC-I) score compared with placebo was from the combined intervention with risperidone and parent training: -11.16 (-15.13, -7.18), followed by risperidone: -7.59 (-9.22, -5.95), and aripiprazole: -5.59 (-7.18, -4). The largest effect on Clinical Global Impression-Improvement (CGI-I) scores was from risperidone, 7.65 (2.17, 27.04), followed by aripiprazole, 7.02 (1.92, 25.72), compared with placebo. Risperidone (4; 1.57, 10.21) and aripiprazole (2.77; 1.20, 6.39) had significantly higher odds ratios for adverse effects, but aripiprazole showed the least weight gain. ConclusionsCombined parent training and risperidone followed by risperidone and aripiprazole showed the best effects on the ABC-I score, whereas risperidone and aripiprazole showed the greatest effect on the CGI-I score. However, risperidone and aripiprazole showed significantly increased adverse effects.

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Impact of Age on Heroin Intravenous Self-Administration in Wistar Rats

Taffe, M. A.; Mehl, S. L.; Grant, Y.; Vandewater, S. A.

2026-05-10 pharmacology and toxicology 10.64898/2026.05.05.723054 medRxiv
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BackgroundEvidence suggests steeper accelerating opioid-related overdose, and non-medical use rates, in middle aged men in recent years compared with younger cohorts. Little is known about whether this is driven by age-related differences in the effects of opioids compared with socio-cultural factors driving non-medical consumption. Rodent models can be useful for dissociating biological from psychosocial factors, however, only minimal evidence exists on the effects of opioids in middle-age rats. ObjectiveTo determine if the anti-nociceptive and rewarding effects of opioids differ between adult and middle-age rats. MethodsFemale and male Wistar rats were obtained in early adulthood and examined across 4 to 11 months of age for nociceptive responses to heroin (0-1.56 mg/kg, s.c.) using a warm-water tail withdrawal assay. Subgroups (N=8 per group) were initiated on intravenous self-administration (IVSA) of heroin at either 5 months or 12 months of age. ResultsAnti-nociceptive effects of heroin did not differ across age. Female rats that initiated IVSA in early adulthood or middle-age obtained significantly more infusions of heroin than male rats of the same age during acquisition, and in dose-substitution under a FR1 schedule. Male, but not female, rats that initiated IVSA in middle age self-administered less heroin then rats that initiated in early adulthood; this was observed in acquisition and in dose-substitution. DiscussionThis study shows that opioid reward is diminished in middle aged male rats. It also found that middle age rats can be used effectively to model opioid-related outcomes, including drug seeking using the IVSA procedure.

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Home-Based Transcutaneous Auricular Vagus Nerve Stimulation for Generalized Anxiety Disorder: Safety, Feasibility, and Preliminary Clinical Outcomes in a Single-Arm Prospective Study

Mosayebi Samani, M.; Zahirmardi, E.; Hedayat fard, S.; Azerians, S.

2026-06-03 psychiatry and clinical psychology 10.64898/2026.06.02.26354707 medRxiv
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Background: Generalized anxiety disorder (GAD) is associated with substantial psychological burden, autonomic dysregulation, and limitations of existing pharmacological and psychotherapeutic treatments. Transcutaneous auricular vagus nerve stimulation (taVNS) has emerged as a promising non-invasive neuromodulation approach, but evidence regarding home-based application in GAD remains limited. Objective: To evaluate the feasibility, safety, and preliminary clinical and physiological outcomes of a home-based taVNS intervention in adults with psychologist-confirmed moderate-to-severe GAD. Methods: In this prospective single-arm feasibility study, 48 participants initiated a 4-week home-based taVNS intervention consisting of two daily stimulation sessions performed five days per week. Clinical assessments were conducted at baseline, Week 2, Week 4, and follow-up visits at Weeks 6 and 8. Ambulatory electrocardiographic monitoring was performed before treatment initiation, at Week 2, and at the end of treatment to assess heart rate variability (HRV) using the root mean square of successive differences (RMSSD). Primary outcomes included feasibility, safety, adherence, and change in clinician-rated anxiety severity (HAM-A). Results: Thirty-four participants completed the study and were included in the primary analyses. HAM-A scores decreased significantly from baseline to Week 4 ([EMD] -6.9, 95% CI -10.4 to -3.4, p = 0.001), with partial maintenance during follow-up. Improvements were also observed in Beck Anxiety Inventory scores, whereas changes in GAD-7, perceived stress, depressive symptoms, and sleep quality were not statistically significant. RMSSD increased significantly from baseline to Week 4 (EMD 6.7 ms, 95% CI 2.1-11.3, p = 0.009). Greater increases in RMSSD were associated with larger reductions in HAM-A (R^2 = 0.18, p = 0.031) and BAI scores (R^2 = 0.21, p = 0.019). No serious adverse events occurred. Mean adherence was 79.8%, and 73.5% of participants completed at least 70% of prescribed stimulation sessions. Conclusions: Home-based taVNS was feasible and generally well tolerated in adults with moderate-to-severe GAD. Preliminary improvements in clinician-rated anxiety severity and autonomic physiological measures were observed; however, the single-arm design precludes causal inference. These findings support further evaluation of home-based taVNS in adequately powered randomized sham-controlled trials.

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Connectivity-guided accelerated theta burst stimulation as augmentation for inpatient treatment-resistant depression: a randomized, double-blind, sham-controlled trial

Mueller, C.; Onken, M.; Hildebrandt, A.; Cash, R. F. H.; Kiebs, M.; Zalesky, A.; Scheele, D.; Hurlemann, R.

2026-07-06 psychiatry and clinical psychology 10.64898/2026.06.25.26356553 medRxiv
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This study examined whether connectivity-guided accelerated intermittent theta-burst stimulation (iTBS) improves depressive symptoms beyond routine multimodal inpatient care in hospitalized patients with treatment-resistant depression (TRD). In this randomized, double-blind, sham-controlled trial, patients with unipolar TRD received active or sham iTBS. Stimulation targeted an individualized left dorsolateral prefrontal cortex site showing most functional anticorrelation with the subgenual anterior cingulate cortex on resting-state functional MRI. Treatment was delivered as 3 daily sessions over 10 weekdays (30 sessions; 54,000 pulses) as an inpatient augmentation strategy. Primary and secondary outcomes were changes in Montgomery-Asberg Depression Rating Scale (MADRS) and Beck Depression Inventory-II (BDI-II) scores during the 2-week stimulation phase. Exploratory endpoints included response and remission rates. Of the 57 randomized patients, 51 completed treatment (active, n=27; sham, n=24). The cohort exhibited moderate-to-severe treatment resistance (mean Maudsley Staging Method score, 10.9) and high psychiatric comorbidity. Active iTBS was associated with significantly steeper MADRS improvement than sham (-3.54 points/week; 95% CI, -5.53 to -1.55; PFDR=.02), corresponding to model-estimated reductions of 12.06 versus 4.98 points with a large effect size (d=-0.89). BDI-II trajectories similarly favored active treatment, though with a smaller effect (group-by-time estimate, -0.23 points/day; 95% CI, -0.41 to -0.05; PFDR=.04; d=-0.22). MADRS response rates were higher with active iTBS (42.3% vs 13.0%), while remission rates were numerically but not significantly higher (26.9% vs 12.5%). No serious adverse events occurred. In conclusion, connectivity-guided iTBS produced significant add-on antidepressant effects during acute inpatient treatment of TRD. Larger multicenter trials are needed to establish durability and optimize implementation.

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Sex Differences in Acute Responses to Psychedelics: Evidence for Greater Subjective Intensity and Impairment in Female Participants

Mason, N. L.; Haijen-Bongers, E. C.; Kuypers, K. P. C.; Frick, A.; Toennes, S. W.; Mallaroni, P.; Ramaekers, J. G.

2026-07-13 neuroscience 10.64898/2026.07.08.737179 medRxiv
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BackgroundSerotonergic psychedelics are advancing as psychiatric treatments, yet acute responses vary between individuals and the contribution of sex, a fundamental biological variable, remains largely unexamined. MethodsWe pooled two double-blind, placebo-controlled studies in healthy volunteers (N = 72; 31 male, 41 female) comparing psilocybin 15 mg, 2C-B 20 mg, and LSD 50 {micro}g. Linear mixed models tested sex differences in acute subjective effects (visual analogue scales), retrospective altered-states ratings (5D- and 11-ASC), empathy (Multifaceted Empathy Test), and peak plasma blood concentrations (Cmax, AUC), with treatment, sex, their interaction, as fixed factors, and age as a covariate. ResultsFemale participants reported numerically higher subjective ratings than male participants on most measures. After adjustment for age, sex differences remained significant for feeling under the drugs influence, reduced vigilance, and impaired control and cognition, with medium-to-large effects. These effects were largely consistent across the three drugs. No sex differences emerged on any empathy measure or in peak drug concentrations. ConclusionsFemale participants may experience more intense acute subjective effects and greater perceived impairment under psychedelics, independent of age and not explained by drug exposure. These preliminary findings, implicating pharmacodynamic rather than pharmacokinetic mechanisms, have implications for dosing, informed consent, and safety monitoring, and underscore the need to treat sex as a biological variable in adequately powered psychedelic trials.

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Personality factors and childhood adversity in psychiatric patients with and without recent suicide attempts: a cross-sectional study

Colic, L.; Musslick, J.; Zerekidze, A.; Bahlmann, L.; Buske, B.; Walter, M.; Jollant, F.; Wagner, G.

2026-05-26 psychiatry and clinical psychology 10.64898/2026.05.25.26354029 medRxiv
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Background: Childhood adversity (CA) is recognized as a distal risk-factor for suicide attempts (SA) in individuals with psychiatric disorders. However, not all individuals with experiences of CA will engage in SA. Contributing to this relationship may be proximal factors such as impulsivity, inward anger and self-aggression. However, these factors are often conceptually blended and measured in different samples. We sought to clarify association among CA and personality factors in persons with SA. Methods: Participants from two studies comprised individuals with a diagnosed psychiatric disorder and history of SA (n= 139) and individuals with depressive disorder (clinical controls, CC; n= 24). We investigated self-reported levels of CA, impulsivity, inward anger, and self-aggression between the SA and CC (pcorr< .012). We tested the relationship among the factors using regression (pcorr<.017) and mediation model (indirect effects, p<.05) within the SA group. Sensitivity models were run controlling for age, gender, symptom severity, trait anger, and externally oriented aggression. Results: SA group had higher impulsivity (pcorr=.067) in a model controlled for age and gender. Other factors did not differ among groups. Within the SA group the analyses revealed positive association among CA and personality factors (pcorr<.06) in basic and model with age and gender, however the association was not specific for internally (self) oriented factors (coefficient comparison, p<.07). Parallel mediation model indicated that CA had indirect effect on self-aggression through impulsivity (p=.001) and to a lesser extent through inward anger (p=.066). Generally, models controlling for cognitive depression symptoms showed less prominent effects (pcorr>.1). Limitations: The study was cross-sectional and did not include behavioral tasks (state) measures of proximal factors. Conclusions: CA and personality factors showed similar severity levels among the SA and CC groups suggesting they may relate to broader psychopathologies, rather than specifically to SA. The association of CA with anger and aggression was unspecific to internally oriented factors indicating the need for more precise measuring instruments developed specifically for individuals with SA. Overall, the study highlights personality factors as being associated with risk in broader vulnerable populations.

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Temporal Trajectories of Motor and Cognitive Dysfunction After Combined PTSD and TBI in Mice: Implications for Neurodegenerative Disease Vulnerability

McDaniel, K. L.; Tinsley, C. E.; Dovek, L.; Potter, Z.; Nungaray, L. R.; McGuire, N. M.; Loeung, J.; Wickham, P. T.; Elliott, J. E.; Meshul, C. K.; Lim, M. M.

2026-06-08 animal behavior and cognition 10.64898/2026.06.03.729686 medRxiv
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Post-Traumatic Stress Disorder (PTSD) commonly occurs alongside Traumatic Brain Injury (TBI), yet the chronic behavioral consequences of combined neurotrauma (i.e., PTSD and TBI) across the sexes remain unclear. Using a mouse model combining Single Prolonged Stress (SPS) as a model for PTSD and Controlled Cortical Impact (CCI) as a model for TBI, we assessed gait, anxiety-like behavior, and contextual fear learning and extinction at 2, 4, and 12-weeks post-injury. Combined neurotrauma produced early and persistent gait impairments in both sexes, delayed changes to anxiety-like behavior characterized by reduced avoidance of an anxiogenic environment, and long-lasting contextual fear recall deficits. Impaired learning was observed in males, where they demonstrated reduced fear acquisition and diminished extinction rates at later time points while females showed no deficits. Across testing and sex, peak deficits emerged at 4 weeks post-neurotrauma. Together, these findings define a sex- and time-dependent behavioral phenotype following combined neurotrauma and underscore the importance of modeling comorbidity to capture the temporal and neurobehavioral consequences of trauma exposure that more closely reflect clinical populations.

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β-Blockers for ED Presentations with Recent Cocaine Use: A Systematic Review

Paterson, T.; Katraj, S. V. K.; Van Wyk, A.; Pooranachandran, V.

2026-06-05 pharmacology and toxicology 10.64898/2026.06.02.729530 medRxiv
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BackgroundCocaine produces cardiovascular toxicity through intense sympathetic stimulation and direct myocardial injury, generating presentations ranging from hypertension and tachycardia to coronary vasospasm, arrhythmia, and myocardial depression. {beta}-blockers are foundational therapies in acute coronary syndromes, yet their use after cocaine exposure remains controversial due to concerns about unopposed -adrenergic stimulation. MethodsA systematic review was conducted in accordance with PRISMA guidelines. PubMed and Google Scholar (2000-2026) were searched for observational studies of adults ([&ge;]18 years) presenting to acute care with recent cocaine use that compared outcomes between {beta}-blocker recipients and non-recipients. Eligible studies reported in-hospital mortality, myocardial infarction/troponin rise, clinically significant arrhythmia, or haemodynamic instability. Risk of bias was assessed using the Newcastle-Ottawa Scale, and certainty of evidence using GRADE. ResultsFour retrospective ED cohorts (n = 1,140) met inclusion criteria; 503 patients received at least one {beta}-blocker dose. Across studies, {beta}-blocker use was not associated with increased in-hospital mortality or malignant arrhythmias. Myocardial infarction was heterogeneous and sensitive to definition and timing. Haemodynamic data showed no hypertensive surge and modest systolic blood pressure reductions. Risk of bias was moderate, and certainty of evidence very low to low. ConclusionsIn typical ED presentations of recent cocaine use, {beta}-blocker administration does not appear to increase mortality, myocardial infarction, or malignant arrhythmias, and available haemodynamic data do not support a reproducible unopposed- response. However, mechanistic and preclinical evidence suggests potential harm in severe intoxication or myocardial depression. A selective, phenotype-guided approach is warranted, and prospective mechanistic studies are needed. Key PointsO_LIBeta-blockers did not increase deaths, heart attacks, or dangerous heart rhythms in adults who came to the emergency department after recent cocaine use. C_LIO_LIBlood pressure generally decreased after beta-blocker treatment, and no consistent "unopposed alpha" reaction was seen in typical presentations. C_LIO_LICaution is still needed in severe intoxication or cases with heart muscle weakness, but for most emergency presentations, beta-blockers appear safe when used appropriately. C_LI

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Stroboscopic Light Stimulation in Adults Reporting Depressive Symptoms: Safety, Tolerability, Feasibility, and Active-Comparator Development in a Staged Early-Phase Study

Nacker, D.; Kalus, L.; Seth, A. K.; Stone, J. M.; Lawson, G.; Simpson, J.; Sander, J. W.; bremner, s.; Jones, C. I.; Wood, W.; Macpherson, F.; Proeckl, D.; Winkler, E.; Schwartzman, D. J.

2026-06-22 psychiatry and clinical psychology 10.64898/2026.06.17.26355864 medRxiv
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Stroboscopic light stimulation (SLS) is a candidate non-pharmacological intervention that induces transient visual and affective experiences, with potential application in depression. Before efficacy testing, clinical development requires safety, tolerability and feasibility data. We report a staged, single-site programme in adults reporting depressive symptoms. Work Package (WP) 1 tested 11 SLS parameter sets for safety and tolerability. An interim bridge study assessed whether a low-phenomenology SLS control reduced subjective visual effects while preserving session context. WP2 randomised 84 participants to four weekly supervised 31-minute sessions of the intervention or a low-phenomenology control. In WP1, 31 participants were analysed; no severe adverse reactions occurred, mean discomfort was low (0.49/10), and the highest session-level upper 80% confidence limit was 1.13/10, well below the prespecified threshold. The interim study supported experiential separation between intervention and control. In WP2, endpoint data were available for 70/84 participants (83.3%): 39/42 in the intervention arm and 31/42 in the control arm. Overall retention met the criterion, but lower control-arm retention remains a design issue; protocol adherence was high, discomfort remained low, and no serious SLS-attributable adverse events occurred. Exploratory depressive-symptom changes suggested a possible BDI-II signal, but do not establish efficacy. Supervised SLS met key safety, tolerability, and feasibility criteria, and a lower visual-phenomenology active control can be carried forward, while masking and comparator credibility remain to be established. The next step is a diagnostically defined, CTU-governed Phase 2a feasibility trial that pre-registers a locked protocol and tests masking, credibility, retention and endpoint precision.

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Selective encoding failure of self-face identity in subthreshold depression

Wen, M.; Su, B.; Chen, Y.; Gu, T.; Qin, P.

2026-05-07 neuroscience 10.64898/2026.05.04.721614 medRxiv
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Subthreshold depression is associated with significant functional impairment and elevated risk of major depressive disorder. A negative self-concept may disrupt the implicit positive association evoked by ones own face, impairing incidental encoding of self-relevant information. Whether subthreshold depression involves a selective deficit in encoding self-face identity remains unclear. The attribute amnesia paradigm is well suited to address this question because it can dissociate attentional selection from working memory encoding. Using this paradigm, we examined the issue across two experiments. Experiment 1 employed nonsocial stimuli (animal drawings) and confirmed an intact attribute amnesia effect in subthreshold depression (n = 30) comparable to healthy controls (n = 30), ruling out a generalized encoding deficit. Experiment 2 replaced targets with faces (self or other) and revealed a selective enhancement of the attribute amnesia effect for self-face identity in subthreshold depression. Specifically, on the surprise trial, accuracy for self-face identity dropped to near-chance levels in the subthreshold depression group, whereas no such deficit emerged for other-faces or in controls. Encoding recovered rapidly once explicit memory expectations were introduced, indicating intact basic encoding capacity. These findings suggest that subthreshold depression is associated with a specific impairment in incidentally encoding self-face identity. This impairment likely stems from a negative self-concept that weakens self-face salience under incidental encoding conditions. By capturing this selective encoding failure, the present study reveals that the self-processing deficit in subthreshold depression can arise at the gating stage between attention and working memory consolidation.