Figure 3.

Repeated amphetamine treatment reduces the magnitude of the inhibitory effect of D₁ receptor stimulation on the I_NaT. A, Representative traces of I_NaT, elicited by a change in voltage command (−70 to −20 mV), before and during application of the D₁ receptor full agonist SKF 81297 onto neurons from saline- and amphetamine-pretreated animals. B, Plot of relative peak I_NaT current as a function of time. Application of SKF 81297 reversibly suppressed peak I_NaT (21.4%; example taken from a saline control rat demonstrating a drug effect time course). C, Bar graph summary of the percentage of inhibition of peak I_NaT by SKF 81297 application onto neurons from saline- and amphetamine-pretreated animals (**p < 0.001). Error bars indicate SE. SAL, Saline; AMPH, amphetamine.