Cardiovascular effects produced by nitric oxide-related drugs in the caudal ventrolateral medulla.
The role of nitric oxide in the central control of blood pressure was evaluated by interfering with its local formation in the caudal region of the ventrolateral medulla (CVLM). Urethane anesthetized male Wistar rats were used. Microinjection of L-arginine (L-Arg, 25-100 nmol) produced a hypertensive effect without significant changes in heart rate (HR). Microinjection of N(G)-nitro-L-arginine methyl ester (L-NAME, 7.4 nmol) produced a significant hypotensive effect. Microinjection of L-Arg (50 nmol) combined with L-NAME (7.4 nmol) did not significantly change mean arterial pressure or HR. A similar finding was obtained with microinjection of L-Arg (50 nmol) 5 min after microinjection of methylene blue (5 nmol) into the CVLM. The pressor effect of L-Arg was also abolished by prior i.v. injection of a vasopressin V1 receptor antagonist, but not by prior i.v. injection of prazosin. These results suggest an inhibitory role for local NO in the CVLM and that nitrergic pathways at the CVLM participate in the central regulation of AVP release.
Lage
R C
RC
Departamento de Fisiologia e Biofísica, ICB-UFMG, Belo Horizonte, MG, Brazil.
Campagnole-Santos
M J
MJ
Fontes
M A
MA
Santos
R A
RA
D000758:Anesthesia; D000818:Animals; D065092:Antidiuretic Hormone Receptor Antagonists; D000959:Antihypertensive Agents / Q000494:pharmacology; D001120:Arginine / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D002560:Cerebrovascular Circulation / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects*; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects / Q000502:physiology*; D008845:Microinjections; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D052250:Nitric Oxide Synthase Type III; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar
D065092:Antidiuretic Hormone Receptor Antagonists; D000959:Antihypertensive Agents; D009569:Nitric Oxide; D001120:Arginine; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; C496316:Nos3 protein, rat; D019331:NG-Nitroarginine Methyl Ester; D011224:Prazosin