title: Neuropeptide Y potentiates contraction and inhibits relaxation of rabbit coronary arteries.
abstract: The effects of neuropeptide Y (NPY) on contraction and relaxation of isolated rabbit coronary arteries were studied. NPY alone caused a weak contraction of coronary arteries with a mean EC50 value of 29 +/- 2.0 nM. Following exposure of coronary arteries to 30 nM NPY, the potencies of norepinephrine (in the presence of 3 microM timolol) and histamine in causing contraction were increased twofold, with no change in maximal contraction. After half-maximal contraction of coronary arteries with histamine and addition of 30 nM NPY, relaxation produced by norepinephrine (in the presence of 3 microM phentolamine), adenosine, and acetylcholine was inhibited. Concentration-response curves for all vasodilators were shifted to the right 10-22-fold by 30 nM NPY. Maximal relaxation caused by adenosine and norepinephrine was not changed by NPY, whereas the maximal response to acetylcholine was 37% less in the presence of NPY. Correlation of the tension produced by NPY with the shift in agonist contraction or relaxation concentration-response curves indicated that NPY-induced increases in baseline tone had no effect on the degree of shift in agonist concentration-response curves. These results show that NPY causes a modest potentiation of agonist-induced contraction and a dramatic blockade of vasodilator-induced relaxation of rabbit coronary arteries.
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000241:Adenosine / Q000494:pharmacology; D000818:Animals; D003331:Coronary Vessels / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D005260:Female; D006632:Histamine / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009478:Neuropeptide Y / Q000494:pharmacology*; D009638:Norepinephrine / Q000494:pharmacology; D011817:Rabbits; D014661:Vasoconstriction / Q000187:drug effects*; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D009478:Neuropeptide Y; D006632:Histamine; D000241:Adenosine; D000109:Acetylcholine; D009638:Norepinephrine