ABSTRACT
Intranasally administrated natural opioid peptide beta-casomorphin-7 (doses 0.001, 0.005, 0.02, and 0.1 mg/kg) was shown to produce alterations in behavior of male albino rats. The anxiolytic effect of the peptide tested in two "open field" modifications was most pronounced. Besides, two higher doses of promoted learning under conditions of negative reinforcement. The beta-casomorphin-7 effects on pain sensitivity and locomotion were insignificant. The obtained results only in part coincide with the effects of intraperitoneal peptide injection described earlier. This suggests that the specific effects of beta-casomorphin-7 considerably depend on the way of its penetration into a body; in case of intranasal administration they are apparently determined by primarily influence of the peptide on hypothalamic structures.