[The behavioral effects of beta-casomorphin-7 and its des-Tyr analogs]

The effects of intraperitoneal administration of the heptapeptide beta-casomorphin-7 (beta-K-7) and its des-Tyr analogues (beta-K-6 and beta-K-4) on spontaneous locomotor activity were investigated in rats using "Opto-Varimax", "RODEO-2" and "open field" tests. At 20 mg/kg 5 minutes prior to the beginning of measurements beta-K-7 produced a significant decrease in linear locomotion and rearing. As for beta-K-6 and beta-K-4, their influence on locomotion of the experimental animals was less evident. In contrast to beta-K-7, its des-Tyr analogues (20 mg/kg) produced a marked decrease in nose-poking behavior. Beta-K-7 in doses that had no effect on spontaneous behaviour (1 and 5 mg/kg) attenuated extreme behavioural displays under stress conditions. The experimental results suggest the advisability of further investigations of neurotropic properties of beta-K-7 and related peptides.