The arylpiperazine derivatives N‐(4‐cyanophenylmethyl)‐4‐(2‐diphenyl)‐1‐piperazinehexanamide and N‐benzyl‐4‐(2‐diphenyl)‐1‐piperazinehexanamide exert a long‐lasting inhibition of human serotonin 5‐HT₇ receptor binding and cAMP signaling

摘要

Abstract We performed a detailed in vitro pharmacological characterization of two arylpiperazine derivatives, compound N ‐(4‐cyanophenylmethyl)‐4‐(2‐diphenyl)‐1‐piperazinehexanamide (LP‐211) previously identified as a high‐affinity brain penetrant ligand for 5‐hydroxytryptamine (serotonin) type 7 (5‐HT₇) receptors, and its analog N ‐benzyl‐4‐(2‐diphenyl)‐1‐piperazinehexanamide (MEL‐9). Both ligands exhibited competitive displacement of [3H]‐(2 R )‐1‐[(3‐hydroxyphenyl)sulfonyl]‐2‐[2‐(4‐methyl‐1‐piperidinyl)ethyl]pyrrolidine ([3H]‐SB‐269970) radioligand binding and insurmountable antagonism of 5‐carboxamidotryptamine (5‐CT)‐stimulated cyclic adenosine monophosphate (cAMP) signaling in human embryonic kidney (HEK293) cells stably expressing human 5‐HT₇ receptors. They also inhibited forskolin‐stimulated adenylate cyclase activity in 5‐HT₇‐expressing HEK293 cells but not in the parental cell line. The compounds elicited long‐lasting (at least 24 h) concentration‐dependent inhibition of radioligand binding at 5‐HT₇‐binding sites in whole‐cell radioligand binding assays, after pretreatment of the cells with the compounds and subsequent compound removal. In cAMP assays, pretreatment of cells with the compounds rendered 5‐HT₇ receptors unresponsive to 5‐CT and also rendered 5‐HT₇‐expressing HEK293 cells unresponsive to forskolin. Compound 1‐(2‐biphenyl)piperazine (RA‐7), a known active metabolite of LP‐211 present in vivo, was able to partially inhibit 5‐HT₇ radioligand binding in a long‐lasting irreversible manner. Hence, LP‐211 and MEL‐9 were identified as high‐affinity long‐acting inhibitors of human 5‐HT₇ receptor binding and function in cell lines. The detailed in vitro characterization of these two pharmacological tools targeting 5‐HT₇ receptors may benefit the study of 5‐HT₇ receptor function and it may lead to the development of novel selective pharmacological tools with defined functional properties at 5‐HT₇ receptors. e00013.