Figure 4.
Intrinsic time course of D2-receptor activation of GIRK current. a, Dopamine (100 μm) evoked GIRK currents from nucleated patches. Increasing the duration of application produced an increase in amplitude. Applications ranging from 5 to 100 ms did not change the time course of the outward current as indicated by the currents after being scaled to the peak. Application of dopamine for 250 ms activated a larger current that reached a peak later than currents induced by short applications of dopamine. b, Summary illustrating the increase in amplitude for 5 ms (n = 9), 100 ms (n = 14) and 250 ms (n = 13) applications of dopamine. c, Summary illustrating the time to peak after application of dopamine (100 μm) for various durations. Horizontal dark gray bar represents the mean ± SEM of the time to peak of IPSC evoked from a single pulse. d, Representative traces illustrating the effect of cocaine on D2-IPSCs. Low concentrations of cocaine (100 nm) increased the amplitude but not the time to peak of the IPSC (n = 9), while higher concentrations (500 nm, n = 8) further increased the amplitude and also the time to peak.