NEUROPEPTIDE-Y INDUCES AND MODULATES VASOCONSTRICTION IN INTRACRANIAL AND PERIPHERAL VESSELS OF ANIMALS AND MAN

Neuropeptide Y (NPY) has recently been reported to coexist with noradrenaline (NA) in central as well as peripheral noradrenergic nerves. NPY-containing nerve fibres are particularly numerous around blood vessels. Studies were performed on isolated pial arteries as well as on arteries and veins from several peripheral vascular beds from rabbits, cat and man. NPY induced a varying degree of direct contraction of the vessels with an EAm up to 15 mN. Pial arteries were more sensitive than peripheral arteries to NPY (mean EC50 = 7.6 .times. 10-9M). The presence of NPY did not cause any consistent or significant potentiation of the contractile response to NA in any of the vessels tested. Transmural electrical stimulation of the perivascular nerves (including blockade with tetrodotoxin) was performed mainly with auricular artery from the rabbit. Blocking experiments confirmed that the neurogenic contraction was mediated by noradrenergic-type fibres. NPY caused a concentration-related potentiation of the neurally evoked contractile response. The peptide also potentiated the tetrodotoxin-resistant probably non-neurogenic contractions obtained during enhanced electrical field stimulation. It is concluded that NPY interacts with NA during sympathetic nerve activation primarily through a presynaptic effect.