Neuropeptide Y is a cotransmitter with norepinephrine in guinea pig inferior mesenteric vein
ABSTRACT Neuropeptide Y (NPY) is a cotransmitter with noradrenaline in guinea pig inferior mesenteric vein. Tyrosine hydroxylase-like immunoreactivity and NPY-like immunoreactivity were colocalized in a dense network of fibers within the adventitial layer of guinea-pig inferior mesenteric vein. Vasoconstrictor responses to electrical field stimulation (0.2–64 Hz, 0.1 ms, 12 V, for 10 s) appear to be mediated primarily by norepinephrine at 0.2 to 4 Hz and by NPY at 8 to 64 Hz. NPY Y1 receptors mediate the contractile responses to both endogenous and exogenous NPY. Norepinephrine and NPY are involved in neuromuscular transmission in guinea pig mesenteric vein suggesting that the sympathetic nervous system requires the coordinated action of norepinephrine and NPY to serve capacitance.
- Annals of the New York Academy of Sciences 02/2006; 839(1):35 - 40. · 4.38 Impact Factor
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ABSTRACT: Neuropeptide Y (NPY)-immunoreactive nerve fibers were numerous around arteries and few around veins. NPY probably co-exists with noradrenaline in such fibers since chemical or surgical sympathectomy eliminated both NPY and noradrenaline from perivascular nerve fibers and since double staining demonstrated dopamine-beta-hydroxylase, the enzyme that catalyzes the conversion of dopamine to noradrenaline, and NPY in the same perivascular nerve fibers. Studies on isolated blood vessels indicated that NPY is not a particularly potent contractile agent in vitro. NPY greatly enhanced the adrenergically mediate contractile response to electrical stimulation and to application of adrenaline, noradrenaline or histamine, as studied in the isolated rabbit gastro-epiploic and femoral arteries. The potentiating effect of NPY on the response to electrical stimulation is probably not presynaptic since NPY affected neither the spontaneous nor the electrically evoked release of [3H]noradrenaline from perivascular sympathetic nerve fibers.Regulatory Peptides 05/1984; 8(3):225-35. · 2.06 Impact Factor
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ABSTRACT: The effect of neuropeptide Y (NPY) on periarterial nerve stimulation-induced release of norepinephrine (NE) and increase in perfusion pressure in the perfused mesenteric arterial bed of the rat was examined. Perfusate effluents were continuously collected and assayed for endogenous NE by high-pressure liquid chromatography (HPLC) coupled to electrochemical detection. Perfusion pressure was continuously monitored by means of a pressure transducer. Periarterial nerve stimulation (8 or 16 Hz, 60 V, 2-ms duration for 30 s) resulted in a readily detectable increase in NE release and perfusion pressure that was attenuated by the prior administration of tetrodotoxin (TTX) (10(-5) M) or guanethidine (5 X 10(-5) M). NPY exerted both prejunctional and postjunctional effects on noradrenergic neurotransmission in this preparation. The peptide produced a concentration-dependent reduction in the release of NE over a concentration range of 10(-10) - 10(-7) M. A similar inhibition effect occurred at 8, 10, and 16 Hz. In contrast, low concentrations (10(-10) and 10(-9) M) decreased the effect of nerve stimulation on perfusion pressure, whereas higher concentrations (10(-7) M) produced a marked potentiation. The alpha 2-adrenoceptor antagonist, yohimbine, did not alter the inhibitory effect of NPY on evoked NE release or the effect on perfusion pressure. Prazosin similarly did not alter the inhibitory effect of NPY on NE release but prevented the increase in perfusion pressure. We conclude that NPY modulates noradrenergic neurotransmission in the mesenteric arterial bed by decreasing the evoked release of NE and producing a concentration-dependent biphasic response on vascular smooth muscle.(ABSTRACT TRUNCATED AT 250 WORDS)Journal of Cardiovascular Pharmacology 01/1988; 10(6):716-22. · 2.38 Impact Factor