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ADRENOCEPTORS OF THE GUINEA‐PIG URINARY BLADDER
Author(s) -
DAVE K.C.,
DHATTIWALA A.S.
Publication year - 1976
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.1476-5381.1976.tb07690.x
Subject(s) - phenoxybenzamine , propranolol , isoprenaline , guinea pig , endocrinology , medicine , chemistry , inhibitory postsynaptic potential , stimulation , urinary bladder , acetylcholine
1 Adrenaline, noradrenaline and isoprenaline (5 μg/ml) did not affect the resting tone of the isolated urinary bladder of the guinea‐pig. 2 The catecholamines (1–2 μg/ml) inhibited neuronally evoked contractions at various stimulation frequencies; the inhibition was maximum at 2 Hz and minimum at 50 Hz. Isoprenaline produced maximum inhibition. 3 Propranolol (0.5 μg/ml) completely blocked the catecholamine‐induced inhibition at all the frequencies employed. The concentration‐response curves of isoprenaline at 2, 10 and 50 Hz were characteristically shifted by propranolol (50 ng/ml). Phenoxybenzamine (0.2 μg/ml) was totally ineffective. 4 In some experiments adrenaline significantly raised the tone of the bladder exposed to propranolol; this effect could be blocked by phenoxybenzamine. 5 Acetylcholine‐induced bladder contractions were inhibited by adrenaline (2 μg/ml); the inhibition was completely blocked by propranolol (0.5 μg/ml). 6 The results indicate the presence of an inhibitory β‐adrenoceptor and suggest the possibility of an excitatory α‐adrenoceptor in guinea‐pig urinary bladder.