Chronic and Acute Intranasal Oxytocin Produce Divergent Social Effects in Mice

Intranasal administration of oxytocin (OXT) might be a promising new adjunctive therapy for mental disorders characterized by social behavioural alterations such as autism and schizophrenia. Despite promising initial studies in humans, it is not yet clear the entity or the specificity of the behavioural effects induced by chronic intranasal OXT and if chronic intranasal OXT could have different effects compared to single administration. This is critical for the aforementioned chronic mental disorders that might potentially involve life-long treatments. Here, we report that chronic intranasal OXT treatment in wild-type C57BL/6J adult mice produced a selective reduction of social behaviors concomitant to a reduction of the OXT receptors throughout the brain. Conversely, acute intranasal OXT treatment produced partial increased in social behaviours especially towards opposite-sex novel-stimulus female mice. Finally, even prolonged exposure to intranasal OXT treatments did not alter, in wild-type animals, parameters of general health such as body weight, locomotor activity, olfactory and auditory functions, nor parameters of memory and sensorimotor gating abilities. These results indicate that a prolonged over-stimulation of a "healthy" oxytocinergic brain system, with no inherent deficits in social interaction and normal endogenous levels of OXT, might results in specific detrimental effects in social behaviours.