Glutamate receptors in the dorsal hippocampus mediate the acquisition, but not the expression, of conditioned place aversion induced by acute morphine withdrawal in rats.

Abstract

To evaluate the role of glutamate receptors in the dorsal hippocampus (DH) in the motivational component of morphine withdrawal. NMDA receptor antagonist D-AP5 (5 microg/0.5 microL per side) or AMPA receptor antagonist NBQX (2 microg/0.5 microL per side) was microinjected into DH of rats. Conditioned place aversion (CPA) induced by naloxone-precipitated morphine withdrawal were assessed. Preconditioning microinjection of D-AP5 or NBQX into the DH impaired the acquisition of CPA in acute morphine-dependent rats. However, intra-DH microinjection of D-AP5 or NBQX after conditioning but before the testing session had no effect on the expression of CPA. Our results suggest that NMDA and AMPA receptors in the dorsal hippocampus are involved in the acquisition, but not in the expression, of the negative motivational components of acute morphine withdrawal in rats.