Erowid References Database
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McNall SJ, Mansour TE.
“A Novel Serotonin Receptor In The Liver Fluke Fasciola Hepatica.”.
Federation Proceedings. 1983;42(7):1876.
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Abstract
[3H] Lysergic acid dlethylamide (LSD) was used as a radioligand to characterize serotonin (5-HT) receptors in membrane particles of Fasciola. The distribution of receptors in the fluke and their specificity for 5-HT antagonists suggest that they are identical to the receptors coupled to adenylate cyclase that we have previously described (Northup, J.K. & T.E. Mansour, in Aol.Pharmocol. 14:804-819, 1978). The relative affinities of a series af 5-HT antagonists ta the fluke receptors were LSD=2-bromo-LSD > methiothepin cyproheptadine=metergoline mianserin=5-HT> spiroperidol> ketanserin. This potency order differs significantly from the 5-HT1 and 5-HT2 receptors reported in the mammalian brain (Peroulka, S.J. and S.H. Snyder, Mol.Pharmocol. 16:687-699, 1979), and suggests that the fluke receptors may represent a new type of 5-HT receptor. Particles prepared from intact flukes preincubated with 5-HT showed no reduction in both [3H]-LSD binding and 5-HT-stimulated adenylate cyclase activity. The desensitization was apparently due to a preferential loss of high affinity receptors for 5-HT. A similar desensitization response occurred directly in fluke particles upon the addition of ligand. In contrast to the reversal of desensitization in intact flukes which required overnight incubation, cell-free desensitization was rapidly reversed following the removal of ligand. The novel characteristics of the fluke receptor, while of general interest to the study of 5-HT action, may also provide a new approach for the development of chemotherapeutic agents against these parasites.
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