| Abstract | We have compared the vasopressor response of alpha-adrenoceptor agonists in young (2 month-old) and older (12 month-old) pithed rats both in the presence and absence of triiodo-L-thyronine (T3)-induced hyperthyroidism. There was no age-related changes in the pressor response to either the alpha 1-selective agonist phenylephrine or the alpha 2-selective agonists clonidine and UK-14,304. However, T3-induced hyperthyroidism caused a selective reduction in postjunctional alpha 2-adrenoceptor-mediated pressor responses but not alpha 1-adrenoceptor-mediated ones in both age groups. In contrast to vascular alpha-adrenoceptors, there was an age-related decrease in the number of myocardial alpha 1-adrenoceptor sites measured by specific binding of [3H]prazosin. With thyroid hormone treatment, the density of ventricular alpha 1 receptors was found to be further reduced even in the older rats. These results suggest that thyroid hormone and aging have different influences on the cardiovascular alpha-adrenoceptor system and that these two physiological variables are independently interrelated. |
| Authors | G Tsujimoto, K Hashimoto
(Affiliation: Department of Pharmacology, Yamanashi Medical College, Japan.)
|
| Journal | Japanese journal of pharmacology
(Jpn J Pharmacol)
Vol. 44
Issue 4
Pg. 437-45
(Aug 1987)
ISSN: 0021-5198 JAPAN |
| PMID | 2824894
(Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
|
| Chemical References |
- Antihypertensive Agents
- Quinoxalines
- Receptors, Adrenergic, alpha
- Prazosin
- brimonidine
- Triiodothyronine
|
| Topics |
- Aging
(metabolism)
- Animals
- Antihypertensive Agents
(pharmacology)
- Blood Pressure
(drug effects)
- Cardiovascular System
(metabolism)
- Decerebrate State
- Hyperthyroidism
(chemically induced, physiopathology)
- Male
- Myocardium
(metabolism)
- Prazosin
(pharmacology)
- Quinoxalines
(pharmacology)
- Rats
- Rats, Inbred Strains
- Receptors, Adrenergic, alpha
(metabolism)
- Triiodothyronine
(pharmacology)
|
