clozapine and oleylamide

We investigated the effects of oleamide, a fatty acid amide isolated from the cerebrospinal fluid of sleep-deprived cats, on serotonin receptor-mediated signaling in cultured mammalian cells. Oleamide demonstrated opposing effects on 5-HT2A and 5-HT7 receptors, in rat pituitary cells and transfected HeLa cells, respectively. Oleamide caused a potentiation of 5-HT-elicited inositol phosphate formation mediated by the 5-HT2A receptor, but inhibited the effects of 5-HT on cAMP production mediated by the 5-HT7 receptor. In addition, oleamide alone caused a significant increase in cAMP accumulation that was dependent on the presence of the 5-HT7 receptor, but was not blocked by clozapine. These results demonstrate that oleamide can have diverse effects on 5-HT-mediated signal transduction at different subtypes of mammalian 5-HT receptors. Additionally, our data suggest that oleamide may act at an allosteric site on the 5-HT7 receptor and can elicit functional responses via activation of this site.

Topics: Animals; Cats; Cerebrosides; Clozapine; Cyclic AMP; Fatty Acids, Monounsaturated; Fluorescent Dyes; HeLa Cells; Humans; Inositol Phosphates; Oleic Acids; Pituitary Gland; Pituitary Neoplasms; Quaternary Ammonium Compounds; Rats; Receptor, Serotonin, 5-HT2A; Receptors, Serotonin; Recombinant Proteins; Serotonin; Signal Transduction; Sleep Deprivation; Transfection

The effects of oleamide, an amidated lipid isolated from the cerebrospinal fluid of sleep-deprived cats, on serotonin receptor-mediated responses were investigated in cultured mammalian cells. In rat P11 cells, which endogenously express the 5-hydroxytryptamine2A (5HT2A) receptor, oleamide significantly potentiated 5HT-induced phosphoinositide hydrolysis. In HeLa cells expressing the 5HT7 receptor subtype, oleamide caused a concentration-dependent increase in cAMP accumulation but with lower efficacy than that observed by 5HT. This effect was not observed in untransfected HeLa cells. Clozapine did not prevent the increase in cAMP elicited by oleamide, and ketanserin caused an approximately 65% decrease. In the presence of 5HT, oleamide had the opposite effect on cAMP, causing insurmountable antagonism of the concentration-effect curve to 5HT, but had no effect on cAMP levels elicited by isoproterenol or forskolin. These results indicate that oleamide can modulate 5HT-mediated signal transduction at different subtypes of mammalian 5HT receptors. Additionally, our data indicate that oleamide acts at an apparent allosteric site on the 5HT7 receptor and elicits functional responses via activation of this site. This represents a unique mechanism of activation for 5HT G protein-coupled receptors and suggests that G protein-coupled neurotransmitter receptors may act like their iontropic counterparts (i.e., gamma-aminobutyric acid type A receptors) in that there may be several binding sites on the receptor that regulate functional activity with varying efficacies.

Topics: Allosteric Regulation; Allosteric Site; Animals; Cats; Cell Line; Cerebrosides; Clozapine; Colforsin; Cyclic AMP; GTP-Binding Proteins; HeLa Cells; Humans; Isoproterenol; Oleic Acids; Phosphatidylinositols; Rats; Receptors, Serotonin; Serotonin; Signal Transduction