Journal of Comparative Neurology

A critical step in visual cortical maturation is refinement of receptive field (RF) size, producing higher acuity vision. This was previously studied using species with well-developed vision (e.g., carnivores, primates), in which visual experience was necessary for refinement but not maintenance of RFs in visual cortex. In contrast, in Syrian hamsters, a crepuscular species with low visual acuity, dark rearing had no effect on RF refinement in juveniles, but RFs re-enlarged in adulthood, resulting in reduced acuity. These inter-species differences raise the question of whether the need for visual experience is primarily related to the phylogenetic position of the species or to its ecological niche. Here we report that dark rearing had no effect on development or maintenance of RF properties of visual cortical neurons in nocturnal mice. Mice with lifelong visual deprivation refined and maintained their RF size over time. Furthermore, the development of stimulus direction tuning was unaffected by dark rearing. In contrast, surround suppression, orientation tuning and the sharpness of direction tuning were abnormal in dark reared mice. These and our previous results from hamsters show that species living in an ecological niche with minimal daylight exposure require little to no visual experience to develop and maintain refined RFs. This study is an important step in developing a better understanding of the role of visual experience in the development of visual processing circuitry and suggests that diurnal mammals may be a better model for human visual cortical development than mice.

The intestinal mesentery has been recently classified as a 'new' organ and contains various cell types including adipocytes, preadipocytes, endothelial cells, and immune cells. In addition, neuronal cell bodies are found in the small intestinal mesentery and are situated either individually or clustered together with glial cells in small ganglion structures close to the gut wall. However, little is known about the origin or function of these extra-intestinal mesenteric neurons. The aim of this study was to better these characterize mesenteric neurons and to examine their connectivity with the ENS using calcium imaging in adult mouse ileum with the mesentery attached. Here we show that neurons in the mesentery express typical ENS neurochemical markers, respond to 5-HT, ATP and the nicotinic agonist DMPP, and receive nicotinic synaptic inputs. Furthermore, using labeling with the neuronal tracer DiI, some mesenteric neurons were found to project into the gut wall and can provide functional excitatory inputs to myenteric neurons. By contrast, we did not find evidence for mesenteric neurons providing inputs to other extrinsic neuronal targets, suggesting that they preferentially interact with the ENS. We also demonstrate that mesenteric neurons can be activated by intestinal distension and that the mesentery provides a source of inhibition to the myenteric plexus. Taken together, we show that the ENS not only interacts with vagal and spinal afferents, and sympathetic and parasympathetic nerves, but also neurons situated in the mesentery. Finally, our data suggest that these neurons may provide a form of negative feedback to the myenteric plexus such as in the event of intestinal distension. These findings have important implications for the regulation of intestinal motility in physiological and pathophysiological conditions.

Extensive experiments document that SPARCL1, a secreted protein that is produced primarily by astrocytes in brain and endothelia throughout the body and that is also known as Hevin, enhances synapse formation. However, the mode of action of SPARCL1 at synapses remains unclear owing to divergent results in the literature. Here, we use cultured neurons from newborn male and female mouse embryos to show that the C-terminal follistatin-like and Ca2+-binding domains of SPARCL1, which account for only 35% of the total SPARCL1 sequence, are sufficient to potently enhance synapse numbers. SPARCL1 acts at nanomolar concentrations at which SPARCL1 does not robustly bind to neurexins, neuroligins or neurexin/neuroligin complexes but avidly interacts with all teneurins. Strikingly, the follistatin-like domain of SPARCL1 on its own strongly binds to teneurins but is unable to stimulate synapse formation. Only when combined with the SPARCL1 Ca2+- binding domain does the follistatin-like domain induce synapses, suggesting that SPARCL1 enhances synapse numbers by binding to teneurins via its C-terminal follistatin-like domain and by activating synapse formation via its Ca2+-binding domain. SIGNIFICANCE STATEMENTSPARCL1 (also known as Hevin) is a synaptogenic factor that is produced primarily by astrocytes in brain, and that enhances synapse formation. How SPARCL1 acts at synapses, however, remains unclear because divergent results describe its binding partners at synapses and the sequences involved in its synaptogenic activity remain unclear. In the present study, we show that SPARCL1 avidly binds to the presynaptic teneurins adhesion molecules, that this binding is mediated by its small follistatin-like domain, and that its synaptogenic activity requires both its follistatin-like and its Ca2+-binding EC domains. Thus, our results suggest that SPARCL1 is recruited to developing synapses by binding of its follistatin-like domain to teneurins and then induces synapse assembly via its Ca2+-binding domain.

Parental care can have pervasive effects on offsprings neurodevelopment. Parent-offspring interactions are often modulated by the neuropeptide oxytocin, which is responsible for the development of social bonds. The development of the oxytocinergic system is dependent on the quality of parental care during the post-natal phase. However, it is yet unknown how post-natal direct interactions can influence the development of the oxytocinergic pathway. Here we tested how an obligate parental care behaviour, tadpole transport in poison frogs, influences the development of the oxytocinergic pathway. To this end, we quantified whole brain expression of oxytocin receptor and oxytocin precursor throughout three developmental stages of A. femoralis tadpoles, before, during and after tadpole transport. Our results show an overall downregulation during tadpole transport, which indicates that during transport tadpoles enter a dormant state to slow down development until they are placed in water. Interestingly, the expression of oxytocin precursor did not vary between the three developmental stages. This might indicate that oxytocin is being recruited during transport, but does not lead to neurodevelopmental changes. In sum, here we present the first evidence of a dormant state during tadpole transport which might be an adaptive response to the terrestrial reproduction in poison frogs.

The electrophysiological process of auditory transduction in insects remains largely conjecture due to the unknown role of ion channels localised to the cilia, but experimental evidence supports either NompC or Nan-Iav as the auditory mechanotransduction ion channel. Here, we knocked down two key genes that code for the two candidate sound-activated ion channels using dsRNA-mediated RNA interference. We measured sound-evoked activity of the auditory nerve and intracellular electrical currents from the ciliated ending of individual auditory receptors. We found that the sound-evoked nerve activity was reduced in nompC, nan and ift88 knockdown. Using whole-cell patch clamp recordings we found that nompC and nan knockdown resulted in reduced sound-evoked transduction current. Stochastic depolarisations hypothesised to be mediated from one of the candidate mechanotransduction ion channels, either NompC or Nan-Iav, where not affected by knockdown of either channel. The discrete depolarisations are therefore mediated through another unidentified ion channel. We test the hypothesis that discrete depolarisations are graded action potentials that travel toward the soma through noise analysis of the transduction current and analysis of discrete depolarisations to voltage-steps. As a positive control we also knocked down ift88, a protein essential for transporting proteins, including ion channels, along the cilium and found both the transduction current and the discrete depolarisations decreased. Key pointsO_LIInjection of dsRNA decreased RNA of nompC and nan C_LIO_LISound-evoked nerve activity is reduced for RNAi-mediated knockdown of nompC and nan C_LIO_LINompC and Nan both contribute to the transduction current C_LIO_LIThe stochastic discrete depolarisations are not due to NompC or Nan-Iav ion channel but to a third unidentified ion channel. C_LIO_LINoise analysis of the transduction current and the discrete depolarisations suggests they are graded action potentials that travel in the direction of the soma. C_LIO_LIKnockdown of ift88 reduced both the transduction current and discrete depolarisations. C_LI Significance StatementInsects are important to understand, economically, agriculturally and medically. However, we still do not understand fundamental aspects of how insects detect their own body movements, vibrations and sound. These senses are detected by insect chordotonal organs, specialised miniaturised mechanoreceptors that convert movements into electrical signals through specialised ion channels. Previous experimental work has advocated either NompC or Nan-Iav as the mechanosensitive ion channel. Here, for the first time, we reduced the expression of both nompC and nan and measured the sound-evoked transduction current directly from neurons in a specialised auditory chordotonal organ. In contradiction to previous studies, we show that both ion channels contribute to the transduction current and find that electrical signals termed "discrete depolarisations" travel toward the soma.

Developmental experience can produce lasting changes in neural function and behavior. Zebra finch offers a powerful model for identifying the molecular mechanisms underlying this process. Both juvenile male and female zebra finches perform developmental sensory song learning that influences their adult behaviors: in males, the structure of the song they sing and in female, the song preferences they exhibit (females cannot sing). The auditory forebrain, a region distinct from but connected to nodes of the male singing circuitry, is required for male sensory song learning. Song experience induces epigenetic, genomic, molecular, cellular and systems-level alterations in the auditory forebrain of males. Much less evidence is available for females. Although epigenetic and molecular data implicate the auditory forebrain in female sensory song learning, there has been no causal test of its role. Further, molecular evidence indicates the potential for distinct mechanisms for male and female sensory song learning, even though they learn during a largely overlapping developmental period. We used pharmacological manipulations of the ERK and mTOR cascades in the auditory forebrain of juvenile females during controlled tutoring, and an operant assay for adult song preference, to test the causal role of the auditory forebrain and the two cascades known to be required for male sensory song learning. We demonstrate that the auditory forebrain is required for female sensory song learning, and that while ERK signaling is necessary for both sexes, that of mTOR is sex specific. Results raise implications for alternative molecular cascade cross-talks and protein synthesis processes that successfully support the developmental learning at the same age and brain region.

Developing neuron-replacement therapies for retinal ganglion cells (RGCs) lost to injury or disease requires a deeper understanding of how restriction to cell identity acquisition may be overcome. Previously, we showed that overexpression of Klf4 in late retinal progenitor cells (late RPCs), which are normally restricted from RGC production, is sufficient to produce cells that display a subset of canonical RGC properties including RGC-associated gene expression and morphological features. In the present study, we investigated the transcriptional and epigenetic mechanisms by which Klf4 overexpression influences the fate of cell types generated from late RPCs. scRNA-seq analysis revealed that Klf4 induces transcriptional changes, with some cells exhibiting gene expression profiles similar to those of resident RGCs. In addition, we observed widespread changes in chromatin accessibility, suggesting that KLF4 remodels the chromatin of late RPCs and influences their transcriptional profile. Our findings show KLF4-driven reprogramming of late RPCs, providing insight into progenitor competence and fate specification to an RGC-like identity. These results suggest that KLF4 could be a component in regenerative therapies due to its ability to reprogram and induce RGC genes outside of the normal RGC developmental window.

In contrast to many other developing systems, in which axon pathfinding and synaptogenesis are separated in time, the pioneering axon of the individually identifiable caudal primary motor neuron in embryonic zebrafish forms en passant synapses during its stereotypical ventral growth. How simultaneous synaptic differentiation and axon pathfinding are coordinated is not fully understood. Here we ask what the role of the tac1 gene, coding for the synaptic tachykinin neuropeptides, is in this unique axon differentiation process. The gene is expressed during axon outgrowth and its disruption results in increased branch length of CaP axons and subtle morphological defects of the pre-synapse. These abnormalities are accompanied by a robust [~]1.5-fold increase in motor neuron activity and in spontaneous early contractions in tac1-deficient embryos. Furthermore, pharmacological inhibition of the tachykinin receptor (Tacr1) leads to altered CaP axonal morphology, mimicking the axonal phenotype observed in tac1-deficient zebrafish. These findings suggest that tachykinin neuropeptides modulate formation and activity of en passant synapses and prevent aberrant axon branching during growth of zebrafish motor axons. HIGHLIGHTS- tac1 refines CaP primary motor axon development in zebrafish - Loss of tac1 disrupts presynaptic maturation at the horizontal myoseptum - tac1 mutants show elevated motor neuron activity and spontaneous contractions

Hippocampal ripples are transient, high-frequency oscillations linked to memory replay and consolidation. Ripples are well-characterized in rodents to occur during periods of behavioral inactivity (i.e., sleep, rest), viewed as "offline" states where replay can emerge with limited sensory interference. However, human studies have increasingly observed ripples during active tasks, raising the questions of whether ripple genesis and function have been misunderstood or whether there are fundamental species differences. We propose that low arousal states--predominant during offline sleep and transient during wake--may constitute a common mechanism of ripple genesis that reconciles these observations. We recorded directly from human hippocampus during sleep and wake, measuring arousal via sleep staging, pupillometry, and heart rate. Ripple occurrence consistently tracked low arousal: rates were maximal in NREM sleep, small-pupil wake states, and slow heart rate periods across sleep and wake. This modulation was stronger in anterior than posterior hippocampus and was hippocampus specific: ripple-like activity outside the hippocampus showed an opposite modulation, increasing with high arousal. These results resolve apparent species differences and provide a unifying view of offline periods as arousal dips that can emerge across behavioral states, including transiently during active wake, suggesting hippocampal ripples, and memory consolidation, occur continuously intermixed with cognition.

The medial habenula (MHb) is an epithalamic structure involved in aversive processing and emotional regulation, notable for its marked cellular heterogeneity and high astrocyte density. This cellular composition suggests that astrocytes may play an important role in MHb structure and plasticity, potentially contributing to the regulation of emotional states. The aim of this study is to characterize sex-dependent astrocytic morphology in the MHb and determine how it is modulated by peripheral alterations and direct central manipulations. A high-fat diet (HFD) was used as a model of metabolic stress, and systemic lipopolysaccharide (LPS) administration was used to induce a peripheral inflammatory challenge. At the central level, a chemogenetic approach using Gi-DREADDs under the GFAP promoter allowed selective modulation of astrocytic intracellular signaling independently of peripheral influences. Preliminary results indicate sex-dependent morphological differences in MHb astrocytes across all these experimental conditions, supporting the idea that MHb astrocytes are sensitive to both peripheral and central disturbances and may represent a key cellular substrate linking body-brain interactions with emotional regulation.

The heterotrimeric G-protein transducin (Gt) is among the key proteins mediating phototransduction in rod and cone cells of the vertebrate retina. Even though this protein has been extensively characterized in mammals, little is known about its expression patterns in migratory songbirds. Here we characterised Gt expression in the European robin, a night-migratory songbird known for its light-dependent magnetoreception. The mechanism underlying magnetoreception is not fully understood, but one well-supported hypothesis involves a radical-pair formation in the blue light receptor cryptochrome type 4a. The - and {gamma}-subunits of cone specific transducin have been identified as possible interaction partners of cryptochrome 4a. Therefore, we analysed the expression patterns of various G-protein subunits in bird photoreceptors. Specifically, we combined single cell RNA sequencing and immunohistochemistry, and tested for protein interaction by pulldown, co-immunoprecipitation, and NanoBiT luminescence assays. We show that genes for G-protein subunits GNB1 and GNB3 (coding for Gt{beta}1 and Gt{beta}3, respectively) are predominantly expressed in rods and cones. Among {gamma}-subunits, GNGT2 (coding for Gt{gamma}T2) was the principal isoform in cones, whereas GNG11 (coding for Gt{gamma}11) was associated with rods. In contrast, we did not detect GNG10 (coding for Gt{gamma}10) expression in either photoreceptor type. Interaction assays demonstrated that all three {beta}{gamma} combinations; {beta}{gamma}T2, {beta}{gamma}10, and {beta}{gamma}11, can associate in vitro. These findings indicate that {beta}{gamma} dimer formation in vivo is likely constrained by the photoreceptor-specific expression of the respective subunits. Furthermore, the absence of GNG10 expression in rods and cones does not support a role of this {gamma}-subunit in photoreceptor-based magnetoreception.

Purpose: Photoreceptor Kv2.1/Kv8.2 voltage-gated potassium channels carry an outward potassium current, helping to set the resting membrane potential and to shape dim light responses. Because potassium flux in the outer retina influences extracellular osmolarity and fluid distribution, we hypothesized that Kv2.1/Kv8.2 channels also contribute to fluid homeostasis in this region of the retina. Methods: OCT imaging was performed in Kv8.2 heterozygous (Het) and knockout (KO) mice aged 4-7 weeks under dark- and light-adapted conditions. Light-dark differences in the distance between the external limiting membrane (ELM) and retinal pigment epithelium (RPE) ({Delta}ELM-RPE) were calculated to quantify light-evoked expansion of the subretinal space (SRS). As a secondary outcome, outer nuclear layer (ONL) thickness was also measured under both lighting conditions. Retinal gene expression was assessed by RNA-seq and droplet digital RT-PCR. Retinal protein expression was determined by western blotting and immunolabeling. Results: {Delta}ELM-RPE was significantly reduced in Kv8.2 KO mice compared with Het controls, indicating reduced SRS hydration. ONL thickness exhibited a small but significant light-dark change that was different between genotypes. Transcriptomic analyses revealed upregulation of osmosensitive genes, including osmolyte transporters and aquaporins. AQP1 protein expression in photoreceptors increased. Conclusions: These findings reveal a previously unrecognized role for Kv2.1/Kv8.2 channels in outer retinal fluid homeostasis and support a model in which photoreceptor potassium efflux contributes to osmotic water movement into the subretinal space.

Background: During vertebrate embryogenesis, the isthmic region spans the midbrain hindbrain-boundary of the neural tube and includes an organizer (IsO) that is essential for proper formation of adjacent brain regions, yet the molecular and cellular composition of the isthmic region remains unresolved. Results: We employed combined single-nucleus ATAC-seq and RNA-seq (scMultiome) in 13 and 16 hours-post-fertilization zebrafish embryos to molecularly resolve cell populations in the isthmic region and validated our findings in vivo by RNA fluorescence in situ hybridization. We identified two distinct isthmic cell populations (isthmic midbrain [IsMB] and isthmic hindbrain [IsHB]) that share expression of canonical isthmic genes, but that differ in their expression of midbrain vs hindbrain genes. We also uncovered a previously unrecognized heterogeneity within the IsHB, reflecting a canonical fgf8-expressing population anteriorly (IsO/r0a), and a novel fgf8-negative population posteriorly (r0p). We find that inhibition of Fgf signaling disrupts formation of the isthmic region, leading to loss of isthmic cell populations except a residual population characterized by a mixed neural identity. Conclusions: Using transcriptional and epigenetic characterization, we expand on prior anatomical and genetic analyses of the isthmic region to refine our understanding of its cellular organization and demonstrate that it consists of several subdomains.

Photoreceptor outer segments are sensory cilia whose maintenance depends on a balance between basal disc renewal and tip shedding, controlled by intraflagellar transport and axonemal microtubule organization. Microtubule plus-end proteins regulate microtubule dynamics and are strong candidates for roles in this process. In this study, mCherry-tagged EB1, EB3, and DCX were overexpressed in zebrafish (Danio rerio) cone photoreceptors under a cone-specific promoter. Eyes were examined at 5 and 10 dpf, and eyecup depth, diameter, and cone photoreceptor area were quantified relative to uninjected controls. At 5 dpf, all three constructs produced eyes indistinguishable from those of controls. By 10 dpf, all three constructs significantly increased eye cup depth and cone photoreceptor area. EB1 and DCX also significantly increased eye cup diameter. EB1 and, more severely, EB3 also caused retinal holes, mainly in the retinal pigment epithelium and at the outer nuclear/outer plexiform layer, along with misshapen cells near the inner plexiform layer. DXC did not cause retinal holes, but, like EB1 and EB3, produced enlarged, bulbous cone outer segments. The results show that overexpression of any of the three +TIPs results in a similar eye and photoreceptor overgrowth phenotype, while also producing construct-specific defects: EB1 and EB3 disrupt the broader retinal architecture, whereas DCX produces enlarged eyes. The shared outer segment hypertrophy suggests an imbalance between cargo delivery at the basal end and shedding of the distal tips. The organomegaly may reflect altered progenitor signaling in the ciliary marginal zone.

Visual areas V2 and V4 are critical for the perception of visual forms in primates. Neurons in area V4 of macaque monkeys are often sensitive to the curvature of specific boundary segments within shapes, but it is unknown how curvature tuning is represented in the developing brain. To address this, we recorded multiunit neural activity from areas V2 and V4 of two macaque monkeys, at both 30 and 58 weeks of age, in response to shape stimuli which primarily varied in curvature along a single segment. Observable curvature tuning was adult-like from 30 weeks of age in both V2 and V4. We compared the tuning of sites to shapes presented at multiple positions. We saw evidence of position-invariant tuning in V4, but not in V2. Position invariance in V4 was stable from 30 weeks of age. Finally, we fit two models - a stimulus-centric model of boundary curvature tuning, and a simple linear model based on the spike-triggered average response to all stimuli. We found many sites in both V2 and V4 whose responses could be captured by one or both models, but no evidence of age-related changes in curvature tuning within the space of either model. Our results suggest that the neural representation of curvature in both areas reaches maturity soon after birth, and that object-centric representations of curvature first emerge in V4, not V2.

The morphogenesis of the optic cup provides a robust system for studying how two apposed epithelial monolayers with distinct properties fold and stretch in a coordinated manner to form the primordial eye. While much research has been conducted on the temporal dynamics of retinal neuroepithelium invagination, the spatial organization and stretching of the retinal pigment epithelium has received less attention. The fish species Astyanax mexicanus offers a unique model to examine the mechanisms of optic tissue morphogenesis through a comparative lens, as it exhibits natural variation in eye development between its river-dwelling and cave-adapted morphs. Using quantitative 3D imaging of optic cups from both morphs, we found that RPE morphogenesis involves transient, graded, and anisotropic cell stretching that patterns the epithelium during optic cup shaping. Analyses of RPE nuclear spacing and cell morphology showed that tissue stretching gradually increases along the proximo-distal axis, suggesting maximal tension in the elongated distal RPE cells aligned along the optic cup meridians. Furthermore, nuclear volumes and apical surface areas of RPE cells scaled spatially along the same axis, independently of endoreplication. In the cavefish natural mutant, RPE expansion was delayed by over six hours and proximal stretching exhibited altered isotropy, indicative of disrupted temporal coordination and suggesting modified mechanical constraints. These results demonstrate that RPE morphogenesis is a highly heterogeneous process from a spatiotemporal perspective, offering new insights into the study of the biomechanical principles of eye development in vertebrates. Summary statementThis study reveals the emergence of cell morphology gradients within the retinal pigment epithelium during morphogenesis of the eye in two distinct populations of the same species of fish.

A recent study (Manjarrez et al., 2026) showed that the classification of cortical dendritic spines into stubby, thin, and mushroom subtypes is unstable under rotation. That result criticizes the categorical scheme but leaves an open question. What is the actual structure of spine morphology once the viewing angle is controlled? Here we answer it. We analyzed 228 spines from layer II pyramidal neurons in the H01 nanometer-resolution reconstruction of human temporal cortex. We first quantified the source of instability. We found that rotating dendritic segments by 90 degrees about their axes shifted the apparent spine height and head width in opposite directions across the population, thereby confirming orientation-dependent measurement error. Furthermore, to obtain measurements free of this artifact, we developed the Spine Morphometry Hub (SMH), a 12-point anatomical landmark framework that characterizes each spine in all three orthogonal planes and extracts geometric, voxel-based, and mesh-based metrics. All morphometric distributions were unimodal and right-skewed. Density-based clustering assigned most spines to noise, and a Monte-Carlo test against a discrete two-type null model confirmed that this pattern is incompatible with categorical subtypes. We also confirmed that apical and basal spines were statistically indistinguishable. Unlike previous reports of a spine continuum, all based on orientation-dependent measurements, our framework removes the viewing-angle confound itself, so the continuum we observe cannot be attributed to a projection artifact. Hence, our framework will be useful to quantify dendritic-spine remodeling in neurological disorders, in which spine shape has long been observed but never measured against an orientation-invariant morphometric standard. HighlightsO_LISpine Morphometry Hub (SMH) measures spines free of viewing-angle error C_LIO_LISMH was validated as an orientation-invariant morphometry framework C_LIO_LIRotating dendrites by 90{degrees} shifts spine height and head width oppositely C_LIO_LIAll morphometric distributions are unimodal and right-skewed, not categorical C_LIO_LISMH could be used to quantify dendritic-spine remodeling in neurological disorders C_LI

Vision depends on the transfer of photoreceptor signals through the retina and then to many CNS visual nuclei. While the most common inherited retinal diseases (IRDs) involve defects in rod and/or cone function, another group (referred to as congenital stationary night blindness (CSNB)) results from defects in glutamate release from photoreceptors, or conversion of the glutamatergic signal in bipolar cells. One example results from mutations in the CACNA2D4 gene, which encodes a subunit of the voltage-gated calcium channel that is critical for glutamate release from both rod and cone photoreceptors. Mutations in CACNA2D4 result in a range of phenotypes in human patients, from incomplete CSNB to rod-cone dystrophy. In the CACNA2D4 knockout mouse (2{delta}4-/-), there is slow photoreceptor degeneration, the photoreceptor-to-bipolar cell synapse is disorganized, and the retina lacks scotopic and photopic full-field electroretinogram b-waves; this also results in low visual acuity. Using adult 2{delta}4-/- mice, we show that recombinant adeno-associated virus (rAAV)-mediated gene therapy directed to rod photoreceptors prevents rod degeneration, restores synaptic organization, retinal function, and improves visual acuity under both light- and dark-adapted conditions. This rescue was maintained for up to 14 months post-treatment. Together, our results demonstrate that synaptic structure and function can be restored in the mature mouse retina in a model of complete synaptic disorganization. The results highlight the neuroprotective potential of targeting synaptic organizing proteins in retinal gene therapy.

Cerebral Palsy (CP) is the most common motor disability in childhood, and the most frequent comorbidity is pain. Rabbit kits subjected to prenatal hypoxia-ischemia (HI) exhibit allodynia and an expansion of nociceptive afferents in the lumbar spinal cord at postnatal day (P5). In this study, we examined how HI alters the development of multiple sensory modalities and its effect on psychosocial measures and C-fiber distribution in the spinal cord. To do this, we performed an HI surgery to occlude blood flow to fetal New Zealand White rabbits for 40 minutes, or a sham surgery. We performed von Frey, Hargreaves, and a cold allodynia test at P1, P5, P11, and P18. Additionally, we performed open field, a two-texture preference test, and immunofluorescence assays at P18. HI kits exhibit altered development and allodynia in von Frey and Hargreaves and minor decreased sensitivity in cold allodynia. HI kits spend less time on the aversive side of the two-texture preference apparatus and more time in the center of an open field but a higher ratio of that time immobile. This is accompanied by changes in the distribution of C-fibers in the dorsal horn of the cervical and lumbar spinal cord. A principal components analysis revealed altered nociception and psychosocial changes are important for differentiating between control and HI kits but not distribution of C-fibers. Overall, HI rabbits kits exhibit altered sensory development, allodynia, anxiety-like behavior, and changes to the distribution of nociceptive afferents in the dorsal horn of the spinal cord.

Rising ocean temperatures challenge ectothermic animals to maintain essential behaviors such as movement and feeding. We asked how a complete neuromuscular pathway preserves function when every component process responds differently to warming. In the pyloric system of the crab Cancer borealis, we simultaneously recorded motor nerve activity, muscle membrane potential, and contraction. Warming preserved rhythmic nerve activity and excitatory junctional potentials, but contraction declined and failed first. Fixed low-frequency stimulation, mimicking cold-temperature motor output, resulted in reduced contraction at warm temperatures, whereas higher-frequency stimulation, mimicking warm-temperature motor output, partially restored contraction. Warming hyperpolarized muscle fibers, moving them farther from contraction threshold, but also reduced input resistance, which together limited over-excitability. However, high-potassium stimulation revealed that the muscle contractile machinery remained functional. Thus, warming acts differently across levels, and overlapping compensatory mechanisms help preserve neuromuscular function across a wide range of temperatures. Significance statementCold-blooded animals that live in climates with significant seasonal changes in ambient temperature must have myriad mechanisms to function over a wide range of environmental conditions. We explore the effects of temperature at multiple levels of organization within the stomatogastric system of the crab, Cancer borealis. We find a series of compensatory mechanisms that cooperatively help maintain stable function despite the fact that the motor patterns, neuromuscular junctions and muscle functions are all differently temperature dependent.