N.G. Levitskaya, D.A. Vilensky, N.Yu. Glazova, L.A. Andreeva, A.A. Kamensky, N.F. Myasoedov
ACTH(4-10) analog Semax influences on depression-like behavior of white rats were investigated in forced-swim test and in different modification of learned helplessness model. The peptide was administered intranasally in doses 0.05 and 0.5 mg/kg 15 min before testing. It was shown that Semax had a normalizing influence on rat behavior in the forced-swim test. In learned helplessness model the peptide injected before learning session in dose 0.05 mg/kg did not affect animal behavior, but at dose 0.5 mg/kg Semax increased the number of escape failures when animals were trained in the same conditions in which they received inescapable foot shock. When rats were trained in other experimental conditions Semax injected in dose 0.05 mg/kg weakened negative influence of inescapable stress on learning capability of rats, at dose 0.5 mg/kg the peptide failed to affect the learning of stressed animals. It is possible, that Semax effects in the learned helplessness paradigm are not connected with peptide influence on animal depression level, and defined by its influence on cognitive processes.