[Influence of nitric oxide synthetase inhibitor on the blood pressure action of clonidine in rats].
We are investigating the influence of NO synthetase inhibitor on the clonidine-induced cardiovascular actions in urethane-anesthetized rats. The systemic blood pressure was measured from right femoral artery, heart rate from the pressure pulse under inhalation of O2. Nw-nitro-L-arginine-methylester (L-NAME, 5 mg/kg), NO synthetase inhibitor, administered intravenously increased blood pressure slightly, although decreased heart rate. The responses to L-NAME were stable about 10 min after the injection. Clonidine (5 mg/kg) administered intravenously indicated the transient increase blood pressure and following continuous decrease of blood pressure. The early transient hypertension of clonidine was potentiated by pretreatment with L-NAME and later continuous hypotension was markedly inhibited. While, the early transient hypertension of clonidine was inhibited by pretreatment with L-arginine and later continuous hypotension was potentiated. The hypertension and tachycardia of intravenous tyramine was enhanced by L-NAME. Clonidine administered into the cerebroventricle did not indicate the early transient hypertension, though produced the later continuous hypotension. These results suggest that L-NAME modifies the cardiovascular responses to clonidine and NO may participate in the modulation.
Yatomi
Y
Y
Medicinal Informatics and Research Units, Faculty of Pharmaceutical Sciences, Fukuoka University, Japan.
Hara
S
S
Fukuzawa
M
M
Ono
N
N
Kuroda
T
T
D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology*; D001120:Arginine / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects*; D003000:Clonidine / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D051381:Rats; D017207:Rats, Sprague-Dawley
D000959:Antihypertensive Agents; D004791:Enzyme Inhibitors; D001120:Arginine; D019001:Nitric Oxide Synthase; D003000:Clonidine; D019331:NG-Nitroarginine Methyl Ester