INDUCTION OF LOCOMOTOR-ACTIVITY BY THE GLUTAMATE ANTAGONIST DNQX INJECTED INTO THE VENTRAL TEGMENTAL AREA

DNQX, an antagonist of AMPA/kainate receptors, was injected into the v entral tegmental area (VTA) to test the hypothesis that AMPA/kainate r eceptors in this brain region might be involved in regulation of locom otor activity. Bilateral injection of 1 mu g DNQX into the VTA increas ed locomotor activity. In addition, unilateral injection of DNQX into this site produced contraversive turning, which was potentiated by coa dministration of amphetamine (1 mg/kg, i.p.). These results suggest th at a glutamatergic afferent to the VTA is tonically active in inhibiti ng locomotor activity. The locomotor stimulation produced by DNQX was not associated with a change in DOPAC/DA level in the nucleus accumben s or the striatum. However, the locomotor stimulation produced by DNQX was markedly attenuated following blockade of dopaminergic receptors by haloperidol (0.5 mg/kg, s.c.) or following dopamine depletion induc ed by reserpine plus alpha-methyl-para-tyrosine pretreatment. These re sults suggest that a basal activation of dopaminergic receptors is req uired for expression of the locomotor activity elicited by DNQX.