Predominance of Nootropic or Anxiolytic Effects of Selank, Semax, and Noopept Peptides Depending on the Route of Administration to BALB/c and С57BL/6 Mice

Abstract

Abstract—The pharmacological effects of intraperitoneal (i.p.) and intranasal (i.n.) administration of the peptides selank (300 µg/kg/day), noopept (1 mg/kg/day), and semax (0.6 mg/kg/day), which are known to possess anxiolytic and nootropic properties, were compared by studying the elevated-plus-maze (EPM) behavior of inbred BALB/c and C57BL/6 mice, and studying their effects on NMDA- and mGluII- receptors in the brain. Semax, noopept, and selank administered via both routes improved exploratory activity and reduced anxiety in BALB/c mice, but the anxiolytic efficiency was higher after intraperitoneal injection and the nootropic efficiency was higher after intranasal administration. In C57BL/6 mice, semax, noopept, and selank did not affect the efficiency of exploratory behavior or anxiety after administration via either route, except for i.p. injection of semax, which showed a greater anxiogenic effect compared to intranasal administration. In BALB/c mice, i.p. administration of noopept and i.n. administration of selank increased the density of NMDA-receptors in the hippocampus and i.n. administration of noopept and semax reduced their density, with no effect on mGluII-receptors. In C57BL/6 mice, i.p. semax and i.n. noopept reduced the number of NMDA-receptor binding sites, and i.p. noopept and semax administered via either route reduced the density of mGluII-receptors in the cerebral cortex.