Alcohol Consumption Decreases Oxytocin Neurons in the Anterior Paraventricular Nucleus of the Hypothalamus in Prairie Voles.

BACKGROUND: Alcohol use disorders are associated with dysfunctional social relationships and stress responses. The neuropeptides oxytocin (OT) and vasopressin (AVP) are known to orchestrate or mediate many aspects of social behavior, stress responses, and ingestive behaviors. Because of the overlap between the effects of alcohol and the roles of OT and AVP, we sought to determine whether alcohol consumption altered expression of OT and AVP in the paraventricular nucleus (PVN) of the hypothalamus, one of the key sites for OT and AVP synthesis.
METHODS: Pair-housed adult male prairie voles were allowed to consume 15% ethanol versus water in the home cage continuously (Continuous-Access [CA] group) or every other day for 4 hours (Intermittent-Access [IA] group). Control animals never had access to alcohol. After 7 weeks, animals were sacrificed and their brains were removed and immunohistochemical analysis of OT- and AVP-immunopositive neurons was performed.
RESULTS: OT-immunopositive neurons were significantly decreased in the anterior PVN in the CA but not IA group, relative to Control animals, suggesting that continuous alcohol consumption decreases the number of OT neurons. There was no effect of alcohol consumption on posterior PVN OT neurons, and no effect on PVN AVP neurons.
CONCLUSIONS: These data show that continuous-access voluntary alcohol consumption is associated with decreased OT neurons in the anterior PVN, suggesting that alcohol-induced alterations in the OT system should be investigated as a mechanism for alcohol-related changes in social behavior, stress responses, and exacerbation of alcohol use disorders.