PACAP enhanced AMPA currents in mouse SCN neurons. Whole cell patch clamp recording techniques were used to directly measure currents evoked by AMPA in ventral SCN neurons during the night (ZT 15–17). The voltage -dependence of the AMPA-evoked currents was measured by moving the membrane potential of the cell through a series of voltage -steps before, during, and after treatment with AMPA (25 μM) in the bath. (A) By itself, PACAP (10 nM, 240 sec) did not activate voltage-dependent currents, however, PACAP did increase the magnitude of AMPA-evoked currents. Top panel shows current-voltage relationships for peak current during AMPA treatment recorded using this protocol before and after treatment with PACAP (10 nM, 240 sec). (B) Histograms demonstrating that the effects of PACAP were mimicked by the PAC1 receptor agonist maxadilan and blocked by the antagonist M65. By itself, M65 did not alter the magnitude of the AMPA current (data not shown). In addition, effects of PACAP were mimicked by the AC activator FSK and blocked by the PKA inhibitor H89. By itself, H89 did not alter the magnitude of the AMPA current (data not shown). Asterisks indicate values that are significantly different than those of the AMPA-treated group (P < 0.05).