Affiliation:
1. University of Pavia, 2nd Faculty of Medicine, Department of Internal Medicine and Therapeutics, Section of Pharmacology, Varese, Italy
Abstract
Abstract
The effects on acetylcholine release from the guinea-pig colon of the N-type calcium channel blocker ω-conotoxin GVIA (ω-conotoxin), the L-type calcium channel blocker nifedipine and the putative blocker of T-type channels, flunarizine, have been investigated. Endogenous basal acetylcholine release and electrically (1 Hz, 1 ms, 450 mA)-evoked overflow in the presence of cholinesterase inhibitor were studied. ω-Conotoxin (1–10 nM) and nifedipine (0·03–3 μm) dose-dependently inhibited basal and electrically-evoked acetylcholine release. Maximal inhibition of basal or electrically-evoked acetylcholine release was about 40% for nifedipine and about 75% for ω-conotoxin. The potency of nifedipine was inversely related to the external calcium concentration: its EC50 value in low-calcium medium (0·5 Mm) was as low as 12 Nm. Flunarizine inhibited acetylcholine release only at concentrations higher than 0·2 μm. Our results are consistent with an involvement of N- and L-type calcium channels in the control of the endogenous acetylcholine release from the guinea-pig colon.
Publisher
Oxford University Press (OUP)
Subject
Pharmaceutical Science,Pharmacology
Reference30 articles.
1. Calcium uptake and protein phosphorylation in myenteric neurons, like the release of vasoactive intestinal polypeptide and acetylcholine, are frequency dependent;Agoston;J. Neurochem.,1989
2. Calcium channel binding in nerves and muscle of canine small intestine;Ahmad;Biochem. Biophys. Res. Commun.,1989
3. Evidence that somatostatin enhances endogenous acetylcholine release in the rat hippocampus;Araujo;J. Neurochem.,1990
4. Prevention by nimodipine, a calcium entry blocker, of the effect of α-adrenoceptor blocking agents on noradrenaline release: differential effects of nimodipine on [3H]noradrenaline and [14C]acetylcholine release measured concomitantly from the guinea-pig ileum;Bartfai;Arch. Int. Pharmacodyn.,1986
5. Comparative effects of calcium antagonists on inhibitory junction potentials of circular muscle of guinea-pig ileum;Bornstein;Br. J. Pharmacol.,1985
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