Nitric oxide mediates cat hindlimb cholinergic vasodilation induced by stimulation of posterior hypothalamus.
The aim of this work was to examine whether endothelium-derived relaxing factor (nitric oxide) mediates cat hindlimb cholinergic vasodilation induced by stimulation of the posterior hypothalamus and beta-adrenergic vasodilation by I.V. injection of isoproterenol using an inhibitor of nitric oxide synthesis, NW-nitro-L-arginine methyl ester (L-NAME). Without L-NAME, femoral blood flow velocity (FBV) increased during hypothalamic stimulation by 11.2 +/- 2.2 cm/s (mean +/- SEM) from the baseline value of 8.4 +/- 2.2 cm/s and femoral conductance (FC) increased by 0.084 +/- 0.021 cm/s/mmHg from 0.062 +/- 0.016 cm/s/mmHg, which were abolished by atropine (0.5 mg I.A.). Arterial blood pressure (AP) and heart rate (HR) increased during hypothalamic stimulation (15 +/- 8 mmHg and 22 +/- 6 beats/min). When isoproterenol (1-2 micrograms I.V.) was injected, FBV and FC increased 5.1 +/- 0.56 cm/s and 0.048 +/- 0.005 cm/s/mmHg. With L-NAME (20-100 mg I.A.), the rises in AP and HR during hypothalamic stimulation were unchanged but the increases in FBV and FC were significantly blunted to 5.2 +/- 3.7 cm/s and 0.026 +/- 0.021 cm/s/mmHg. In contrast, L-NAME did not affect the responses in FBV and FC during stimulation of beta-adrenergic receptors. The effect of NG-monomethyl-L-arginine (10-30 mg I.A.) was the same as L-NAME. It is suggested that nitric oxide is involved in hindlimb cholinergic vasodilation neurally induced by hypothalamic stimulation but not in beta-adrenergic vasodilation.
Matsukawa
K
K
Department of Cardiac Physiology, National Cardiovascular Center Research Institute, Suita, Japan.
Shindo
T
T
Shirai
M
M
Ninomiya
I
I
D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D001285:Atropine / Q000494:pharmacology; D002415:Cats; D002799:Cholinergic Fibers / Q000187:drug effects / Q000502:physiology*; D004558:Electric Stimulation; D006439:Hemodynamics / Q000187:drug effects / Q000502:physiology; D006614:Hindlimb; D007034:Hypothalamus, Posterior / Q000502:physiology*; D007545:Isoproterenol / Q000494:pharmacology; D019331:NG-Nitroarginine Methyl Ester; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000502:physiology*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000502:physiology; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*; D019323:omega-N-Methylarginine
D011943:Receptors, Adrenergic, beta; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D001285:Atropine; D001120:Arginine; D007545:Isoproterenol; D019331:NG-Nitroarginine Methyl Ester