[Changes in beta-casomorphine-7 effect on behavior of albino rat pups in postnatal development].

The analgetic effect of heptapeptide beta-casomorphine-7 in newborn albino rats (20 mg/kg, i.p.) was recorded already 14 days after birth in the "hot plate" test. The first signs of a possible influence of the peptide on motor activity were observed only at the age of 28 days. They are expressed in impairment of motor coordination and change in locomotion level ("Opto-Varimex" test). The obtained evidence probably reflect the processes of discrete maturation of different components of the opioid system of the rat brain.