Effects of cervical sympathetic nerve stimulation and neuropeptide Y (NPY) on cranial blood flow in the cat.

Effects of cervical sympathetic nerve stimulation (SNS) at 10 Hz and intravenous infusion of neuropeptide Y (NPY), 10 and 100 pmol x kg body wt-1 x min-1 for 5 min, on regional blood flow in the cat were investigated with radioactive microspheres. Sympathetic nerve stimulation caused significant reductions in blood flows in the facial tissues including the eye. Alpha-adrenoceptor blockade with phenoxybenzamine and combined beta- and alpha-adrenoceptor blockade with propranolol and phenoxybenzamine abolished the effects of sympathetic nerve stimulation in most facial tissues except in the tongue, upper eyelid and masseter muscle. In most cranial tissues, neuropeptide Y reduced regional blood flow and increased vascular resistance. No effect of neuropeptide Y on vascular resistance was observed in the choroid. In the present study, evidence for a non-adrenergic component in sympathetic vasoconstriction was found in the tongue, upper eyelid and masseter muscle but not in the majority of feline facial tissues. Neuropeptide Y was a potent vasoconstrictor in many cranial tissues, while in parts of the uvea, the effects of neuropeptide Y were less pronounced.