Exaggerated Bezold-Jarisch reflex in the hypertension induced by inhibition of nitric oxide synthesis.
The present study was designed to investigate the role of cardiopulmonary reflex, more specifically the Bezold-Jarisch reflex, in experimental hypertension induced by chronic administration of Nw-nitro-L-arginine methyl ester (L-NAME) (0.5 mg/ml) added to the drinking water for 6 days. The study was performed in male Wistar rats (200-350 g), 9 animals per group. L-NAME ingestion caused a significant increase in resting mean arterial pressure (MAP: 182 +/- 4 mmHg) and heart rate (HR: 447 +/- 20 bpm) when compared to untreated rats (MAP: 112 +/- 3 mmHg and HR: 355 +/- 10 bpm). Cardiopulmonary receptors were chemically stimulated with bolus injections of 5-hydroxytryptamine (5-HT, 4-10 micrograms/kg, iv) followed by measuring the falls in diastolic arterial pressure (DAP) and HR in conscious and freely moving animals. As expected, the responses to intravenous injections of 5-HT consisted of a dose-dependent reduction in HR (from 26 +/- 14 to 175 +/- 25 bpm) and DAP (from 7 +/- 4 to 39 +/- 3 mmHg) in the control rats. Both bradycardia and diastolic hypotension were significantly accentuated in the L-NAME animals (approximately 30%). These data suggest that, in contrast to other models of hypertension, in the present one caused by inhibition of nitric oxide synthesis, the Bezold-Jarisch reflex is exaggerated. This neural dysfunction could be related to changes in the cardiac vagal efferent or effector.
Araújo
M T
MT
Departamento de Ciências Fisiológicas, Universidade Federal do Espírito Santo, Vitória, Brasil.
Cabral
A M
AM
Vasquez
E C
EC
D000818:Animals; D001120:Arginine / Q000008:administration & dosage / Q000031:analogs & derivatives*; D001794:Blood Pressure / Q000187:drug effects*; D004791:Enzyme Inhibitors / Q000008:administration & dosage*; D006339:Heart Rate / Q000187:drug effects*; D006973:Hypertension / Q000139:chemically induced*; D019331:NG-Nitroarginine Methyl Ester; D009569:Nitric Oxide / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D051381:Rats; D017208:Rats, Wistar; D012018:Reflex / Q000187:drug effects*; D014661:Vasoconstriction / Q000187:drug effects
D004791:Enzyme Inhibitors; D009569:Nitric Oxide; D001120:Arginine; D019331:NG-Nitroarginine Methyl Ester