Figure 2.

Activation of D1 receptors attenuates sEPSP amplification at depolarized membrane potentials Aa, example traces showing that SKF81297 (5 μm) attenuates the increase in sEPSP area at depolarized potentials but has no effects on sEPSPs recorded at −80 mV. b, summary graph showing the changes in sEPSP area with membrane potential in control conditions and after application of SKF81297 (5 μm). Two factor ANOVA (n = 9 cells) demonstrated a significant effect of membrane potential (F_6,112 = 13.1, P < 0.001) and an absence of significant global effect of SKF81297 application (F_1,112 = 3.74, P = 0.056). However, a significant interaction between membrane potential and SKF91297 (F_6,112 = 2.29, P < 0.05) indicated an effect of SKF81297 that was conditional to membrane potential value. Planned comparisons demonstrated a significant effect of SKF81297 at −50 mV (*P < 0.01) but not at other membrane potentials. Ba, sEPSP area was plotted as a function of time in an example experiment illustrating the relatively rapid time course of the effect of SKF81297, and its partial reversal during washout. The horizontal bar indicates the time during which SKF81297 was applied to the slices. The vertical grey bars indicate the time at which the cells were held near −50 mV or −80 mV. b, bar graphs summarizing the data on the effects of SKF81297 and their partial reversal after 15 min of drug washout. During recordings at −50 mV, single factor ANOVA (n = 9 cells) followed by planned comparisons demonstrated a significant effect of SKF81297 application (*P < 0.02) but absence of significant effect of washout. At −80 mV, no significant differences between group means were found. Ca, example recordings showing that the attenuation of the response to hyperpolarizing steps by SKF81297 was significant only at depolarized membrane potentials. b, bar graph summarizing the effects of D1R activation on the pyramidal cell response to hyperpolarizing current steps at hyperpolarized and depolarized membrane potentials. Two factor ANOVA (n = 9 cells) demonstrated a significant effect of membrane potential (F_1,16 = 11.3, P < 0.005) but no overall effect of SKF81297 application (F_1,16 = 2.84, P = 0.11). However, the significant interaction between factors (F_1,16 = 7.44, P < 0.02) suggested an effect of SKF81297 that was conditional to membrane potential. Planned comparisons showed that SKF81297 had a significant effect at −50 mV (*P < 0.02) but not at −80 mV.