Fig. 1

Effect of dihydroergotamine (DHE) on the vasodepressor CGRPergic outflow in pithed rats. a Original experimental tracings illustrating the vasodepressor responses induced by electrical stimulation of the perivascular sensory CGRPergic outflow during continuous infusions of either methoxamine (control; above) or DHE (below). Note that during continuous infusions of DHE (3.1 μg/kg·min) the vasodepressor responses induced by electrical stimulation were attenuated versus control. In both cases, the vasodepressor responses were selective as no changes in heart rate were observed. Panels (b) and (c) show the vasodepressor responses by electrical stimulation or i.v. bolus injections of α-CGRP, respectively, induced during an i.v. continuous infusions of 3.1 μg/kg·min DHE (n = 5 each). For the sake of clarity, control responses (○) were induced during continuous infusions of methoxamine (20 μg/kg·min). * Significantly different responses (P < 0.05) vs. control. BP, blood pressure; HR, heart rate