Effect of 6-OHDA lesions of the dopaminergic mesolimbic system on drug priming induced reinstatement of extinguished morphine CPP in rats.

OBJECTIVE: To evaluate the role played by mesolimbic dopaminergic system in the reinstatement of drug-seeking behavior induced by priming injections of morphine. METHODS: After the extinguishment of morphine conditioned place preference (CPP), low-dose catecholaminergic neurotoxin 6-hydroxydopamine (6-OHDA) was bilaterally injected into ventral tegmental area (VTA, 1 g.L-1) and nucleus accumbens (NAc, 5 g.L-1) before being primed with low-dose morphine. RESULTS: The effects of drug-priming to induce reinstatement of morphine CPP could be completely abolished by 6-OHDA microinjected into VTA to damage the perikaryon of dopaminergic neurons, or into NAc to lesion the terminal field of the dopaminergic pathway. CONCLUSION: The functional integrality of the mesolimbic dopaminergic system is indispensable for drug priming-induced reinstatement of conditioned place preference.