A1, Traces illustrate spike discharge at the times indicated in A2. A2, Time course of the increase in the ongoing pacemaking firing rate, recorded from a current-clamped DA neuron in the posterior ventral tegmental area (p-VTA) of a rat, by 0.1 µM salsolinol. B1, Traces obtained at the times indicated in B2. B2, Time course of the effect of salsolinol on the firing rate of a DA neuron in the presence of APV (50 µM) and DNQX (20 µM), the antagonists of NMDA and AMPA receptors. C, Summary plot of decease in firing rate by APV + DNQX. D, Summary plot (means ± S.E.M.) of increase in firing rate of p-VTA DA neurons induced by salsolinol (0.1 µM) in ACSF is larger than that in the APV+DNQX. Numbers in bars indicate numbers of neurons tested. *P<0.05, **P<0.01, paired t-test for salsolinol vs. pre-salsolinol control. Unpaired t-test for salsolinol vs. APV+DNQX+salsolinol.