The influence of α-chymotrypsin and diazepam on the phasic (mainly direct) and tonic (indirect, probably substance P-mediated) components of intestinal cholinergic contractions, induced by the GABA-A receptor agonist 3-aminopropane sulphonic acid (3-APS), was investigated in the guinea-pig ileum. α-Chymotrypsin, at a concentration (20 U/ml) not affecting submaximal Ach (0.1 μM) contractions, preferentially depressed the tonic component of the 3-APS (30 μM)-induced response. A brief exposure (10 or 60 sec) to diazepam (0.1 μM) potentiated both the phasic and the tonic contractions evoked by low (10, 30 μM) 3-APS concentration. This potentiation was prevented by bicuculline (30 μM), hyoscine (1 μM) and flumazenil (1, 3 μM). These results provide further support for an involvement of a peptide neurotransmitter on GABA-A receptor-mediated cholinergic response in the ileum. The modulation of this response by diazepam is probably exerted through recognition sites resembling the 'central type' benzodiazepine receptors.
|Number of pages||11|
|Journal||Archives Internationales de Pharmacodynamie et de Therapie|
|Publication status||Published - 1988|
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