Central depressant effects of N3-substituted 6-azauridines in mice

Central depressant effects in mice of N3-substituted 6-azauridines (6-AzUd) (1) were examined by intracerebroventricular (i.c.v.) injection. Eleven derivatives including alkyl-, benzyl-, xylyl- and phenylethyl-substitution onto the N3-position of 1 were synthesized and their pharmacological effects were evaluated using hypnotic activity, locomotor activity, motor incoordination and pentobarbital-induced sleep prolongation as indices. Six of 12 compounds showed the hypnotic activity. At a dose of 2 mumol/mouse, the mean sleeping time induced by 1, N3-benzyl-6-AzUd (7), N3-o-xylyl-6-AzUd (8), N3-m-xylyl-6-AzUd (9), N3-p-xylyl-6-AzUd (10) and N3-alpha-phenylethyl-6-AzUd (11) was 14, 11, 45, 12, 9 and 16 min, respectively. These derivatives and N3-beta-phenylethyl-6-AzUd (12) (1.5 mumol/mouse) significantly prolonged pentobarbital-induced (40 mg/kg, i.p.) sleeping time, whereas none of the N3-alkylated derivatives (methyl-, ethyl-, n-propyl-, n-butyl- and allyl-substitution) exerted the hypnotic activity or pentobarbital-induced sleep prolongation. Nucleoside 1 and its xylyl-derivatives (1.5 mumol/mouse) significantly decreased locomotor activity of mice, their effects paralleled the hypnotic activity. These compounds (1.5 mumol/mouse) also produced motor incoordination and potentiated the effect of diazepam-induced motor incoordination. These results indicate that 1 and its benzyl-related derivatives, but not alkyl-derivatives have a depressant effect on the central nervous system.