Characterization and localization of a peripheral neural 5-hydroxytryptamine receptor subtype (5-HT1P) with a selective agonist, /sup 3/H-5-hydroxyindalpine
Peripheral neural 5-hydroxytryptamine (5-HT) receptors are different from both classes 5-HT1 and 5-HT2, which have been described from studies of 5-HT receptors in the brain. Recently, it has been shown that, as in the CNS, there is more than a single type of neural receptor for 5-HT in the enteric nervous system. One of these, called 5-HT1P, has a high affinity for 3H-5-HT, initiates a long-lasting depolarization of enteric neurons associated with an increase in membrane resistance, and is the physiological receptor through which enteric serotoninergic neurons mediate slow EPSPs. The other receptor, called 5-HT3 (5-HT2P), does not bind /sup 3/H-5-HT with high affinity, and initiates a brief depolarization of enteric neurons with decreased input resistance, but a physiological action of 5-HT mediated by these receptors has not yet been identified. Hydroxylated indalpines have been found to be agonists at 5-HT1P receptors. We have now examined 5-HT1P receptors using 5-hydroxyindalpine (5-OHIP) as a probe. The action of 5-OHIP on enteric neurons was determined electrophysiologically and compared with that of 5-HT; the binding of /sup 3/H-5-OHIP to isolated enteric membranes was studied by rapid filtration, and to frozen sections of tissue by radioautography. /sup 3/H-5-OHIP binding was compared with that of /sup 3/H-5-HT. 5-OHIP, like 5-HT, induced a triphasic response in most enteric neurons: an initial short-lived depolarization, during which input resistance fell, followed by recovery, and then a long-lasting depolarization, during which the input resistance increased. 5-OHIP bound saturably, reversibly, and with high affinity to enteric membranes (Kd = 7.6 +/- 0.7 nM; Bmax = 76 +/- 14 fmol/mg protein).
- Research Organization:
- Columbia Univ., New York, NY (USA)
- OSTI ID:
- 5934552
- Journal Information:
- J. Neurosci.; (United States), Journal Name: J. Neurosci.; (United States) Vol. 8:7; ISSN JNRSD
- Country of Publication:
- United States
- Language:
- English
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59 BASIC BIOLOGICAL SCIENCES
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