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Enhancement of guinea‐pig intestinal peristalsis by blockade of muscarinic M 1 ‐receptors
Author(s) -
Schwörer H.,
Kilbinger H.
Publication year - 1988
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.1476-5381.1988.tb10330.x
Subject(s) - peristalsis , pirenzepine , muscarinic acetylcholine receptor , bicuculline , chemistry , endocrinology , medicine , carbachol , receptor , gabaa receptor , biology , biochemistry
1 The effects of pirenzepine and hyoscine on the peristaltic reflex were investigated in the guinea‐pig isolated small intestine. Peristalsis was induced by raising the intraluminal pressure and the volume of fluid propelled was taken as a measure of the efficiency of peristaltic activity. 2 Low concentrations of pirenzepine (0.1‐1 n m ) and of hyoscine (0.01 n m ) significantly enhanced peristalsis, whereas larger concentrations of both drugs caused inhibition. Pirenzepine was about 6 times less potent than hyoscine in increasing peristalsis, but was about 100 times less potent in inhibiting it. 3 Neither tolazoline (1 μ m ) nor naloxone (0.3 μ m ) affected the stimulatory action of pirenzepine on peristalsis. 4 Bicuculline increased the efficiency of peristalsis at concentrations of 1 μ m and 10 μ m ; at 10 n m , bicuculline reduced significantly the increase of peristalsis by pirenzepine. γ‐Aminobutyric acid (GABA) did not affect peristaltic activity, but the stimulatory effect of pirenzepine was abolished in the presence of 100 μ m GABA. 5 The results indicate that activation of neuronal M 1 ‐receptors causes inhibition of small intestinal peristalsis. Bicuculline‐sensitive ‘GABAergic’ synapses are probably involved in this inhibition.