Possible dependence of pressor and heart rate effects of NG-nitro-L-arginine on autonomic nerve activity.
1. The effects of NG-nitro-L-arginine (L-NNA) on mean arterial pressure (MAP) and heart rate (HR) were investigated in conscious rats. 2. Intravenous bolus cumulative doses of L-NNA (1-32 mg kg-1) dose-dependently increased MAP. Both mecamylamine and phentolamine increased MAP responses to L-NNA, angiotensin II and methoxamine. Propranolol, reserpine, atropine and captopril did not affect MAP response to L-NNA. 3. A significant negative correlation of HR and MAP responses to L-NNA was obtained in control rats but not in rats pretreated with reserpine or mecamylamine. Significant negative correlations also occurred in the presence of atropine, propranolol, phentolamine or captopril. 4. A single i.v. bolus dose of L-NNA (32 mg kg-1) raised MAP to a peak value of 53 +/- 3 mmHg and the effect lasted more than 2 h; the rise and recovery of MAP were accompanied by significant decrease and increase in HR, respectively. While both phentolamine and mecamylamine increased peak MAP response to L-NNA, mecamylamine abolished the biphasic HR response and phentolamine potentiated the bradycardiac component of HR. 5. Blockade of the autonomic nervous and renin-angiotensin systems did not attenuate the pressor effects of L-NNA. However, the biphasic HR response to L-NNA is mediated via modulation of autonomic nerve activities.
Wang
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Department of Pharmacology & Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver, Canada.
Pang
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D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives* / Q000494:pharmacology; D001341:Autonomic Nervous System / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D006339:Heart Rate / Q000187:drug effects*; D019335:Nitroarginine; D010275:Parasympathetic Nervous System / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D013564:Sympathetic Nervous System / Q000502:physiology
D019335:Nitroarginine; D001120:Arginine