Oxytocin treatment in the prelimbic cortex reduces relapse to methamphetamine-seeking and is associated with reduced activity in the rostral nucleus accumbens core.

Addiction to the psychostimulant Methamphetamine (METH) is characterised by high rates of relapse. Currently there are no approved effective pharmacotherapies for METH dependence. The neuropeptide oxytocin (OXY) potently reduces METH-seeking behaviours in rodent models of relapse and is now being used in clinical trials to treat drug-dependent individuals. However, OXY administration in humans may be impeded by its poor penetration of the brain. Therefore, identification of the neural mechanisms by which OXY reduces METH relapse may guide the development of improved OXY-based therapies for METH addiction. Systemic OXY administration is associated with attenuated METH-induced activity in the prelimbic cortex (PrL); a key brain region which exerts control over much of the reward and addiction circuitry. However, it is not known whether OXY acts directly in the PrL to cause reductions in drug-seeking and downstream brain activity. Therefore, the present study sought to determine whether OXY infused into the PrL reduces cue-induced and METH-primed reinstatement and METH-induced neuronal activity in the downstream nucleus accumbens core (NAcc). Male Sprague Dawley rats underwent intravenous METH self-administration, extinction, and subsequent reinstatement tests. OXY was infused bilaterally into the PrL prior to cue-induced (0, 1 μg/side) and METH-primed reinstatement (0, 0.33, 1.0, 3.0 μg/side). Finally, we quantified cFos immunofluorescence in the NAcc as a proxy for downstream neuronal activity following a PrL infusion of OXY (0, 1 μg/side) prior to METH-primed reinstatement. OXY in the PrL significantly reduced both cue-induced and METH-primed reinstatement. Additionally, intra-PrL OXY reduced METH-induced cFos expression in the rostral but not caudal pole of the NAcc. These findings demonstrate OXY action in the PrL in reducing METH-seeking behaviours and METH-induced activity in the reward circuit. Furthermore, these results suggest that the therapeutic effects of systemically administered OXY on reducing METH-seeking behaviours may involve the PrL-NAc pathway.