Age-related decrease in centrally-mediated pressor response to clonidine in conscious rats.
An age-related change in pressor response to intracerebroventricular (i.c.v.) injection of clonidine in conscious rats was investigated. In 15-week-old rats, clonidine (2 to 20 micrograms) caused a dose-dependent pressor response concomitant with decrease in heart rate. The depressor response to i.c.v. clonidine at lower doses (2 and 5 micrograms) but not higher doses (10 and 20 micrograms) was observed. The pressor response to clonidine in 20- and 30-week-old rats was markedly diminished, and the depressor response appeared at any of the doses injected. However, no age-related change in heart rate responses was observed. These results suggest that the centrally mediated pressor response to clonidine is age-related and masks the depressor response.
Kawasaki
H
H
Department of Clinical Pharmaceutical Science, Faculty of Pharmaceutical Sciences, Okayama University, Japan. kawasaki@pheasant.pharm.okayama-u.ac.jp
Araki
H
H
Futagami
K
K
Gomita
Y
Y
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000375:Aging / Q000502:physiology*; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects*; D001921:Brain / Q000502:physiology*; D003000:Clonidine / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004569:Electroencephalography; D006339:Heart Rate / Q000187:drug effects; D007276:Injections, Intraventricular; D008297:Male; D051381:Rats; D017208:Rats, Wistar
D000316:Adrenergic alpha-Agonists; D000959:Antihypertensive Agents; D003000:Clonidine