Binding of 5-hydroxytryptamine analogs by isolated<i>Spisula</i>sperm membrane

Abstract

Summary Serotonin receptors were identified in Spisula sperm membranes by radioligand binding assay. Sperm membranes were prepared by nitrogen cavitation and by density gradient ultracentrifugation. Specific binding of [3H]5-HT to the receptors of isolated sperm membranes was determined. The dissociation constant was 2.7 nM and the maximum binding capacity was 11.25 pmoles/mg of protein. The order of decreasing potency of 5-HT agonists in blocking [3H]5-HT binding to the sperm membrane was as follows: 2-methyl 5-HT> 8-OH-DPAT> 5-HT> 5-CT> α-methyl-5-HT; and that of 5-HT antagonists was: ICS-205-930> BMY-7379> mianserin> methysergide. These findings suggest that the 5-HT receptors in Spisula sperm membranes contain sites that interact with 5-HT3 and 5-HT1 analogs.