Possible involvement of K(ATP) channel activation in depressor responses to vasoactive neuropeptides in rats

I.v. bolus injections of vasoactive intestinal polypeptide (VIP) (0.3 or 1 microg/kg), calcitonin gene-related peptide (CGRP) (0.3 microg/kg) or substance P (0.1 microg/kg) to anesthetized rats reduced blood pressure, accompanied by slight increases in heart rate. Cromakalim (0.3 microg/kg/min) infused i.v. significantly potentiated the depressor responses to VIP and CGRP, but not those to substance P and acetylcholine (ACh) (0.1 microg/kg). Glibenclamide (20 mg/kg, i.v.) significantly inhibited not only the depressor responses to VIP and CGRP, but also the augmentation of the effects of the two agents by cromakalim. These results suggest that the depressor responses to VIP and CGRP are mediated in part through K(ATP) channel activation.