[Substituted 2,3,4,5-tetrahydro-1H-gamma-carbolines: new antagonists of histamine H1 receptors].

The properties of 2,3,4,5-tetrahydro-1H-gamma-carbolines containing acid, ether, and amido-substituents, were assessed as potential antagonists of histamine H1 receptors (H1R), capable of blocking histamine-induced calcium fluxes in SK-N-SH cells. The structure--activity relationship for their antagonistic activity is discussed. Among the gamma-carbolines used in the study, the antihistamine activity considerably depends on the nature of substituents in positions 2, 5, and 8 of the heterocycle. The most active antagonist, ethyl 3-(2-methyl-8-fluoro-2,3,4,5-tetrahydro-1H-gamma-carboline-5-yl)propionate, with high affinity to the H1R (Ki = 6.5 nM), produces no adverse effects on motor activity of mice in doses 1-40 mg/kg, which shows the absence of a sedative effect.