Neuropeptide tyrosine (NPY)-induced potentiation of the pressor activity of catecholamines in conscious rats.
IV bolus administration of 2.5-50 micrograms NPY (0.6-12.5 nmol) to conscious rats produced a dose- and time-dependent increase in systolic and diastolic blood pressure. Following priming with 2.5 micrograms NPY, or larger doses, the subsequent administrations of noradrenaline produced pressor responses that were potentiated both in magnitude and duration. The NPY-induced potentiation of the pressor response to noradrenaline was dose-dependent and extended to the pressor action of adrenaline and angiotensin II but not to the hypotensions produced by bradykinin or isoproterenol. The potentiation was not related to the fact that multiple doses of catecholamines were repeated. Reserpine did not substantially modify the NPY-induced potentiation of the pressor activity of the catecholamines. Chemical sympathectomy following 6-hydroxydopamine caused a marked supersensitivity to the catecholamines and NPY but obliterated the NPY-induced potentiation of the pressor effect of adrenaline. Nifedipine reduced the pressor action of the catecholamines and NPY but did not attenuate the NPY-induced potentiation of the pressor action of catecholamines. It is concluded that the acute pressor effect of NPY and of the potentiation of the catecholamine pressor effects involve different mechanisms.
López
L F
LF
Department of Physiology, Faculty of Biological Sciences, Catholic University, Santiago, Chile.
Pérez
A
A
St-Pierre
S
S
Huidobro-Toro
J P
JP
D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004837:Epinephrine / Q000494:pharmacology*; D018738:Hexamethonium; D006584:Hexamethonium Compounds / Q000494:pharmacology; D006892:Hydroxydopamines / Q000494:pharmacology; D008297:Male; D009478:Neuropeptide Y / Q000494:pharmacology*; D009543:Nifedipine / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology*; D016627:Oxidopamine; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values; D012110:Reserpine / Q000494:pharmacology
D000959:Antihypertensive Agents; D006584:Hexamethonium Compounds; D006892:Hydroxydopamines; D009478:Neuropeptide Y; D018738:Hexamethonium; D012110:Reserpine; D016627:Oxidopamine; D009543:Nifedipine; D009638:Norepinephrine; D004837:Epinephrine