Central nitric oxide attenuates the baroreceptor reflex in conscious rabbits.
We examined the role of central nitric oxide (NO) in the baroreceptor reflex in conscious rabbits. Intracerebroventricular infusion of 20 mumol of N omega-nitro-L-arginine methyl ester (L-NAME) to block central NO resulted in increases in arterial pressure, renal sympathetic nerve activity (RSNA), and plasma catecholamine levels, and the pressor response was suppressed by pretreatment with pentolinium (5 mg/kg i.v.). On the other hand, a subpressor dose of intracerebroventricular L-NAME (10 mumol/h) caused significant increases in baroreflex sensitivities assessed by RSNA and heart rate compared with vehicle infusion [maximum gain: -18.2 +/- 0.9 vs. -9.6 +/- 0.9%/mmHg (P < 0.001) and -14.3 +/- 2.3 vs. -5.7 +/- 0.4 beats.min-1.mmHg-1 (P < 0.05), respectively]. Conversely, an intracerebroventricular infusion of Et2N[N(O)NO]Na, an NO donor (1 mumol/h) significantly attenuated the baroreflex sensitivities. However, intracerebroventricular infusion of N omega-nitro-D-arginine methyl ester (10 mumol/h), an enantiomer of L-NAME, failed to alter the baroreflex sensitivities. These results suggest that 1) the pressor response induced by inhibition of central NO synthesis is mainly mediated by the enhanced sympathetic outflow and 2) central NO attenuates the baroreflex control of RSNA and heart rate in conscious rabbits.
Matsumura
K
K
Second Department of Internal Medicine, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Abe
I
I
Tsuchihashi
T
T
Fujishima
M
M
D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D001127:Arginine Vasopressin / Q000097:blood; D017704:Baroreflex / Q000187:drug effects*; D001921:Brain / Q000502:physiology*; D002319:Cardiovascular System / Q000187:drug effects; D002395:Catecholamines / Q000097:blood; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007276:Injections, Intraventricular; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000008:administration & dosage* / Q000494:pharmacology; D009603:Nitroso Compounds / Q000008:administration & dosage / Q000494:pharmacology; D010425:Pentolinium Tartrate / Q000494:pharmacology; D011817:Rabbits; D013564:Sympathetic Nervous System / Q000187:drug effects
D000959:Antihypertensive Agents; D002395:Catecholamines; D004791:Enzyme Inhibitors; C093285:NOC 18; D009603:Nitroso Compounds; D001127:Arginine Vasopressin; D009569:Nitric Oxide; D010425:Pentolinium Tartrate; D019331:NG-Nitroarginine Methyl Ester