Pre- and postjunctional effects of neuropeptide Y on the rabbit isolated ear artery.
1. In the isolated perfused and superfused rabbit ear artery, neuropeptide Y (NPY, 0.3-100 nmol/l) had no direct vasoconstrictor action, but produced a concentration-dependent and reversible enhancement of vasoconstrictor responses to both sympathetic nerve stimulation and exogenous noradrenaline. 2. In arteries in which the noradrenergic transmitter stores had been radiolabelled with [3H]-noradrenaline, 100 nmol/l NPY inhibited the stimulation-induced (1 Hz for 30 s) release of radioactivity, but the lower concentrations tested (10 and 30 nmol/l) had no effect. NPY (10, 30 and 100 nmol/l) had no effect on the resting release of radioactivity. 3. Thus, NPY in low concentrations enhances vasoconstrictor responses in the rabbit ear artery by a postjunctional action; prejunctionally, NPY inhibits stimulation-induced transmitter release when it is present in high concentrations.
Wong-Dusting
H K
HK
Department of Pharmacology, University of Melbourne, Parkville, Victoria, Australia.
Rand
M J
MJ
D000818:Animals; D001158:Arteries / Q000187:drug effects; D004431:Ear, External / Q000098:blood supply; D004558:Electric Stimulation; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000294:innervation / Q000502:physiology; D009411:Nerve Endings / Q000187:drug effects; D009469:Neuromuscular Junction / Q000187:drug effects*; D009478:Neuropeptide Y / Q000494:pharmacology*; D009638:Norepinephrine / Q000378:metabolism / Q000494:pharmacology; D011817:Rabbits; D012039:Regional Blood Flow / Q000187:drug effects; D013564:Sympathetic Nervous System / Q000187:drug effects; D014661:Vasoconstriction / Q000187:drug effects
D009478:Neuropeptide Y; D009638:Norepinephrine