N-methyl-D-aspartate increases the excitability of nigrostriatal dopamine terminals

The terminal excitability of nigrostriatal dopamine cells was measured before and after i.v. administration of N-methyl-D-aspartate (NMDA; 1 or 4 mg/kg), the competitive NMDA antagonist AP-7 (2-amino-7-phosphonoheptanoic acid) (4 mg/kg) or saline. NMDA produced a dose-dependent increase in terminal excitability, in the absence of an effect on the somal membrane, whereas AP-7 and saline were without effect. These data provide convergent in vivo evidence that glutamate can enhance striatal dopamine release via the NMDA receptor.