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Occurrence of α 1s ‐adrenoceptors in the mouse but not in the rabbit isolated anococcygeus preparations
Author(s) -
Coates Jill,
Weetman D.F.
Publication year - 1983
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1983.tb09370.x
Subject(s) - phenoxybenzamine , agonist , lagomorpha , chemistry , receptor , medicine , endocrinology , intrinsic activity , biology , biochemistry
1 Both Sgd 101/75 (4(2‐imidazoline‐amino‐2‐methylindazol‐chlorhydrate) and noradrenaline contracted anococcygeal preparations from the mouse and rabbit. 2 The maximal response to and sensitivity (EC 30 values) of each drug on the mouse was similar, whereas in the rabbit, Sgd 101/75 was a partial agonist relative to noradrenaline (intrinsic activity 0.50) and the EC 30 value was 14.5 times higher than for noradrenaline. 3 In both species, phenoxybenzamine (0.3 n m for 30 min followed by 20 washes over 30 min) reduced the effects of Sgd 101/75 preferentially. When noradrenaline was then added in the presence of a high concentration of Sgd 101/75 (400 μ m ), its maximum response and EC 30 value were decreased in the rabbit, but not in the mouse. 4 When a range of concentrations of phenoxybenzamine (30 p m ‐3μ m for 30 min followed by 20 washes over 30 min) was tested, the maximum response of the rabbit anococcygeus to noradrenaline declined in a concentration‐dependent manner. Similar experiments in the mouse resulted in two distinct sensitivities of the maximum response of noradrenaline to phenoxybenzamine (at 0.3 and 300 n m ). 5 The results indicate that noradrenaline acts on two receptors to contract the mouse anococcygeus (α 1 and α 1s ‐adrenoceptors), but only one (α 1 ‐adrenoceptor) in preparations derived from the rabbit.