Effects of neuropeptide Y on canine cerebral circulation.

The effects of neuropeptide Y (NPY) on the vascular tone of isolated cerebral arteries and vertebral blood flow (VBF) were studied in dogs. NPY elicited a dose-dependent contraction of arteries derived from the brain with ED50 values of 2 nM for the middle cerebral and basilar arteries. Arteries from the neck did not respond to NPY. Intra-arterial administration of NPY as a bolus reduced the VBF dose dependently, with no significant alteration of mean arterial blood pressure and heart rate. The decrease in VBF developed slowly and had a long duration, which was consistent with the observations made in vitro. NPY suppressed the contractile effect of noradrenaline (NA) on isolated cerebral arteries and pretreatment with NPY suppressed the effect of NA on VBF, indicating that NPY contributes to the inhibitory modulation of postsynaptic adrenergic mechanisms. These findings suggest that NPY could have a role in the regulation of cerebral circulation.