Involvement of μ-Receptor in Endogenous Opioid Peptide-Mediated Inhibition of Acetylcholine Release From the Rat Stomach
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We examined the effect of endogenous opioid peptides on vagally evoked release of acetylcholine (ACh) from the isolated, vascularly perfused rat stomach. The vagus nerves were electrically stimulated twice at 2.5 Hz for 2 min, and test substances were administered during the second stimulation. β-Endorphin (10<SUP>-7</SUP> and 3×10<SUP>-7</SUP> M), an endogenous nonselective agonist of μ-receptors, inhibited the release of ACh. However, [Leu<SUP>5</SUP>]-enkephalin, an endogenous nonselective agonist of δ-receptors, and U-50488, a κ-receptor agonist, had no effect at a higher dose of 10<SUP>-6</SUP> M. β-Endorphin-induced inhibition was abolished by naloxone. Endomorphins 1 and 2 (3×10<SUP>-7</SUP> and 10<SUP>-6</SUP> M), endogenous selective agonists of μ-receptors, also inhibited the release of ACh. These results suggest that the μ-receptor is involved in the endogenous opioid peptide-induced inhibition of the release of ACh from the rat stomach.
- The Japanese Journal of Pharmacology
The Japanese Journal of Pharmacology 78(1), 93-95, 1998-09
The Japanese Pharmacological Society