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THE EFFECT OF AGING ON α‐ADRENOCEPTORS AND THEIR RESPONSES IN RABBITS
Author(s) -
Hamilton C. A.,
Dalrymple H. W.,
Jones C. R.,
Reid J. L.
Publication year - 1985
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.1985.tb00906.x
Subject(s) - prazosin , endocrinology , yohimbine , medicine , alpha (finance) , adrenergic receptor , agonist , receptor , clonidine , radioligand , in vivo , chemistry , alpha 2 adrenergic receptor , biology , antagonist , construct validity , nursing , microbiology and biotechnology , patient satisfaction
SUMMARY 1. The effects of age on α‐adrenoceptor responses, sensitivity and number were studied in rabbits aged from 1 to 36 months. 2. Three types of investigation were carried out: conscious animal studies, isolated tissue studies and radioligand binding studies. 3. Specific [ 3 H]‐prazosin binding decreased with age in both spleen and heart suggesting that the number of α 1 ‐receptors declined at least in the tissues studied. The specific binding of [ 3 H]‐clonidine to spleen membranes and [ 3 H]‐yohimbine to platelets was not affected by age. 4. In vitro responsiveness to α‐adrenoceptor agonists decreased with age in abdominal aorta and renal artery, while the affinity of adrenoceptors for prazosin (pA 2 ) was not altered. The decrease may be non‐specific as responses to potassium were also altered. No change in α 2 ‐adrenoceptor mediated platelet aggregation was observed. 5. No change in pressor or depressor responses to full adrenoceptor agonists or to antagonists was observed in vivo. However, responses to clonidine, which is a partial agonist at α 1 ‐adrenoceptors, were decreased. 6. While aging influenced α‐adrenoceptor subtypes differently, there was no direct relation between functional changes and number of receptors.