The enteric neural receptor for 5-hydroxytryptamine |
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Authors: | M D Gershon M Takaki H Tamir T Branchek |
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Institution: | (1) Departments of Anatomy and Cell Biology and Psychiatry, Columbia University, College of Physicians and Surgeons, 630 West 168th Street, 10032 New York, New York, USA |
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Abstract: | Summary An enteric neural receptor for serotonin (5-HT) has been characterized. This receptor was assayed, using3H-5-HT as a radiologand, by rapid filtration of isolated enteric membranes and by radioautography. In addition, intracellular recordings were made from ganglion cells of the myenteric plexus. High affinity, saturable, reversible, and specific binding of3H-5-HT was demonstrated both to membranes of the dissected longitudinal muscle with adherent myenteric plexus and the mucosa-submucosa. Radioautographs showed these3H-5-HT binding sites to be in myenteric ganglia and in a broad unresolved band at the mucosal-submucosal interface. Antagonists active at receptors for other neurotransmitters than 5-HT, at either of the two known types of CNS 5-HT receptor, and at 5-HT uptake sites on serotonergic neurons failed to inhibit binding of3H-5-HT. The structural requirements of analogues for binding to the enteric 5-HT receptor matched the known pharmacology of M or neural 5-HT receptors. A novel 5-HT antagonist was found. This compound, N-acetyl-5-hydroxytryptophyl-5-hydroxytryptophan amide (5-HTP-DP), antagonized the action of 5-HT on type II/AH cells of the myenteric plexus but did not affect the release or actions of acetylcholine (nicotinic or muscarinic) or substance P. 5-HTP-DP was also an equally potent displacer of3H-5-HT from its binding sites on enteric membranes. It is concluded that the sites responsible for specific binding of3H-5-HT are enteric M or neural 5-HT receptors. These receptors differ from those now known to be present in the CNS. |
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Keywords: | 5-hydroxytryptamine serotonin receptors enteric nervous system gut radioautography |
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