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THE EFFECT OF PRAZOSIN ON THE GUINEA‐PIG ILEUM
Author(s) -
FAGBEMI S.O.,
SALAKO L.A.
Publication year - 1980
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.1476-5381.1980.tb08715.x
Subject(s) - phentolamine , phenoxybenzamine , prazosin , yohimbine , endocrinology , medicine , chemistry , stimulation , postsynaptic potential , ileum , pharmacology , propranolol , receptor , antagonist
1 The α‐adrenoceptor blocking activity of prazosin was compared with that of phentolamine, yohimbine and phenoxybenzamine in the guinea‐pig isolated ileum. 2 Phentolamine (2.56 × 10 −8 to 2.56 × 10 −6 m ) and yohimbine (5.12 × 10 −8 to 5.12 × 10 −6 m ) antagonized the sympathetic inhibition of twitches induced by transmural stimulation, whereas prazosin (5.28 × 10 −8 to 5.28 × 10 −6 m ) and phenoxybenzamine (4.2 × 10 −9 to 4.2 × 10 −7 m ) had no effect. 3 Phentolamine, yohimbine, prazosin and phenoxybenzamine antagonized the relaxant response of the ileum to periarterial nerve stimulation and to exogenous noradrenaline in the absence of transmural stimulation. 4 The pA 2 value for phentolamine against noradrenaline in the transmurally‐stimulated gut (presynaptic α‐adrenoceptor site; 8.17 ± 0.04) was significantly different from that in the non‐stimulated gut (postsynaptic α‐adrenoceptor site; 6.88 ± 0.12). 5 Phentolamine and prazosin probably block noradrenaline responses at the same α‐adrenoceptor site on the postsynaptic membrane.