The role of the vasopressin V1A receptor in oxytocin modulation of methamphetamine primed reinstatement.

The neuropeptide oxytocin has shown promise as an effective therapy in pre-clinical models of methamphetamine (METH) addiction. The nucleus accumbens core (NAcc) has been identified as an important site for oxytocin to inhibit METH behaviours, although previous findings suggest that the effects of oxytocin in the NAcc are mediated by receptors other than the oxytocin receptor (OTR). Oxytocin has high affinity for the vasopressin V1A receptor (V1AR) which has been implicated in numerous oxytocin-dependent social behaviours. The aim of this study was to investigate the involvement of the V1AR in mediating the effect of oxytocin treatment to reduce METH-primed reinstatement of METH-seeking behaviour. Male rats were trained to self-administer intravenous infusions of METH by lever press during daily 2-h fixed ratio 1 scheduled sessions for 20 days. Following extinction of lever pressing, rats were tested for the effects of oxytocin alone, oxytocin co-administered with a selective V1AR antagonist, or oxytocin co-administered with a selective OTR antagonist, on METH-primed reinstatement, when administered systemically, or when microinjected into the NAcc. Systemic administration of oxytocin prevented METH-primed reinstatement, an effect which was significantly reduced by systemic pre-treatment with a V1AR but not OTR antagonist. Local administration of oxytocin into the NAcc reduced METH-primed reinstatement, but not when the V1AR was blocked. Our results demonstrate a substantial role for the V1AR in mediating the inhibitory effects of oxytocin on METH-primed reinstatement, and indicate the need for investigations into the differential involvement of V1ARs and OTRs in oxytocin-induced reduction of METH-related behaviours.