Nitric oxide-related inhibition of carotid chemosensory nerve activity in the cat.
The hypothesis that endogenous nitric oxide may play a physiological role in the regulation of carotid chemosensory activity was tested in this study. The nitric oxide synthase (NOS) inhibitors, L-nitro-arginine-methyl ester (L-NAME, 25-200 microM) and NG-monomethyl-L-arginine acetate (L-NMMA, 50 and 100 microM) were used to study its effects on the chemosensory activity of perfused and superfused cat carotid bodies (n = 21) in vitro at 37-37 degrees C. L-NAME elicited slow excitation of the sensory activity as did L-NMMA. The peak-response was dose-dependent, and approached saturation around 200 microM. The excitation by L-NAME showed the following characteristics (mean +/- SEM): latency of response, 2.2 min +/- 0.3 min; time to peak response, 5.5 min +/- 1.0 min and the peak response increased to 407 +/- 42 imp/sec from 88 +/- 13 imp/sec. The peak response was significantly different (P < 0.05) from the baseline activity. L-arginine (50-500 microM) only briefly reversed the stimulation. Hypoxia enhanced the excitation by L-NAME. On the other hand, sodium nitroprusside (SNP, 0.5-10 microM) which supplies NO, terminated the excitatory effect of L-NAME. The results provide evidence in favor of an inhibitory role of endogenous NO in the carotid body, and exogenous application of NO confirms the inhibitory effect.
Chugh
D K
DK
Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia 19104-6085.
Katayama
M
M
Mokashi
A
A
Bebout
D E
DE
Ray
D K
DK
Lahiri
S
S
D000594:Amino Acid Oxidoreductases / Q000037:antagonists & inhibitors; D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D002344:Carotid Body / Q000187:drug effects / Q000502:physiology*; D002415:Cats; D066298:In Vitro Techniques; D019331:NG-Nitroarginine Methyl Ester; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000494:pharmacology / Q000502:physiology*; D019001:Nitric Oxide Synthase; D009599:Nitroprusside / Q000494:pharmacology; D010100:Oxygen / Q000502:physiology; D010477:Perfusion; D019323:omega-N-Methylarginine
D009599:Nitroprusside; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D001120:Arginine; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases; D010100:Oxygen; D019331:NG-Nitroarginine Methyl Ester