Presynaptic modulation by noradrenaline and an opioid of the substance P-induced release of [3H]acetylcholine from the myenteric plexus |
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Authors: | E S Vizi L Bartho |
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Affiliation: | 1. Institute of Experimental Medicine, Hungarian Academy of Sciences, P.O. Box 67, H-1450 Budapest, Hungary;2. Department of Pharmacology, University Medical School of Pecs, H-7643 Pecs, Hungary |
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Abstract: | Substance P (7.5-750 nM) applied in superfusion dose-dependently released 3H from isolated strips of myenteric plexus-longitudinal muscle of the guinea-pig ileum loaded with [3H]choline. Separation of the [3H]acetylcholine and [3H]choline components of the released radioactivity revealed that in response to substance P (SP) administration only the release of [3H]acetylcholine increased above resting level. A slowly developing tachyphylaxis to the effect of SP was observed. Evidence has been obtained that the slow tachyphylaxis developed to the acetylcholine-releasing effect of SP was not due to the exhaustion of releasable acetylcholine pool. Release of acetylcholine by 150 nM SP was completely prevented by tetrodotoxin or in a Ca2+-free medium and greatly reduced in the presence of noradrenaline or the opioid receptor agonist (D-Met2,Pro5)-enkephalinamide. The effect of noradrenaline and the opioid peptide was apparently prevented by yohimbine and naloxone, respectively. |
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Keywords: | enteric nervous system opioid receptors acetylcholine release choline kinase technique |
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