Regional differences in the contractile activity of neuropeptide Y, endothelin, oxytocin and vasopressin: comparison with non-peptidergic constrictors. An in vitro study in the basilar and mesenteric arteries of the rat.

The vasoconstrictor effect of the peptides neuropeptide Y (NPY), endothelin (ENDO), vasopressin (VPR) and oxytocin (OXY) (10(-11)-10(-7) M) was compared in the isolated basilar (BAS) and mesenteric (MES) arteries of rat. The contractile activity of these peptides was compared to that of three nonpeptidergic constrictors: noradrenaline (NA), serotonin (5-hydroxytryptamine, 5-HT) and prostaglandin F2 alpha (PGF2 alpha) (10(-8)-10(-4) M). As regards EC50 values, PGF2 alpha was equally potent in both vessels studied, 5-HT was more potent in BAS and NA was without contractile effect in BAS. Pronounced regional differences were found for the peptides studied. BAS was more sensitive in EC50 values to the peptides in the order ENDO > or = VRP > OXY > NPY. In MES, OXY and NPY caused no and VPR caused weak contraction, whereas the effect of ENDO was pronounced, with a similar EC50 value as in BAS. In conclusion, marked regional differences were found in response to contractile agents in the vascular beds studied. Peptidergic constrictor mechanisms might be of large importance in the regulation of cerebral blood flow during physiological or pathophysiological conditions.