[Naloxone-induced suppression of the behavioral manifestation of serotoninergic system hyperactivation by beta-casomorphins-7 in mice].

The effect of human and bovine beta-casomorphins-7 on the behavior of mice under conditions of 5-hydroxytryptophan (5-HT) induced hyperactivation of the serotoninergic system (head twitch test) has been studied. Intraperitoneal administration of each peptide in a dose of 1 mg/kg was shown to suppress the head twitch response in mice approximately by half (p < 0.01). This effect was completely blocked by the opioid receptor antagonist naloxone (10 mg/kg), which did not alter the behavior of mice in the head twitch test by itself. Thus, the influence of casomorphins on the serotoninergic system in vivo has been demonstrated for the first time. The role of 5-HT and opioid receptors in the mechanism of casomorphin action is discussed.