Fig. 4.

Blockade of GRP-evoked phase delays at ZT13 (A) and phase advances at ZT19 (C) by the BB₂ receptor antagonist DPDMBE. In comparison to the phase-resetting effects of GRP alone at ZT13 or ZT19 (Fig. 1C,D), this antagonist did not alter the time of peak mean firing rate at either ZT13 (B) or ZT19 (D) but blocked the phase-shifting effects of GRP at these phases. In each panel, thesolid dots represent the smoothed running mean firing rate in spikes per second, and the vertical bars are the standard error of that smoothed firing rate mean. Filledand unfilled horizontal bars depict projected night and day portions, respectively, of the projected 48 hr period.