A Checking Model of Obsessive-Compulsive Disorder Based on the Hypothalamic Defensive System Against a Potential Threat

BACKGROUNDObsessive-compulsive disorder (OCD) is a psychiatric disorder characterized by obsessive thoughts and compulsive behavior. While some theories imply that OCD patients have cognitive biases and dysfunctional motivation regarding a potential threat, these views are not adequately supported by neurological evidence. Hypothalamic perifornical (PeF) urocortin-3 (UCN3) neurons are involved in defensive responses to a potential threat, and the activation of these neurons in mice induces repetitive and excessive checking and burying of novel objects. In this study, we evaluated the hypothesis that mice in which PeF UCN3 neurons are activated can serve as an OCD model. METHODSPeF UCN3 neurons were chemogenetically activated with clozapine-N oxide (CNO) in Ucn3-Cre mice. Marble-burying activity, repetitive/stereotypic behaviors in the homecage, and excessive responses to a novel object were measured as OCD-like behaviors. The effects of clinically used drugs for treating OCD on these behaviors were evaluated. The effect of CNO on neural activity in the cortico-striato-thalamo-cortical loop (which is regarded as an OCD circuit) was assessed with c-Fos immunolabeling. RESULTSCNO increased marble-burying activity, evoked homecage-specific repetitive/stereotypic behaviors that probably aimed to seal entrances, and induced repetitive and excessive checking and burying of novel objects. These behaviors were suppressed by selective serotonin-reuptake inhibitors but not by diazepam. CNO increased neural activity in the cortico-striato-thalamo-cortical loop. CONCLUSIONSThese results indicated that mice whose PeF UCN3 neurons are activated can serve as a model of OCD, particularly as a checking model. This supports theories concerning the role of potential threats in the pathophysiology of OCD.