Peculiarities of behavioral reactions of albino rats exposed to stress and introduction of non-opiate analogues of leu-enkephalins in the early ontogenic periods

Abstract

The authors studied behavioral reactions of 7-day and 30-day-old albino Wistar rats, exposed to intrauterine hypoxia as well as emotional-pain stress and were introduced peptides - non-opiate analogues of leu-enkephalins in the neonatal periods of ontogenesis. The authors found that exposure to intrauterine hypoxia as well as emotional-pain stumuli led to slowdown of sensor-motor reflexes maturation in 7-day-old animals (duration of turning in the test "Negative geotropism" increased by 66 %); 30-day-old animals in this experimental group demonstrated increased anxiety and "motor disinhibition" in the tests "Elevated plus-maze" and "Open field". Daily introduction from the second to sixth day of life of 100 mkg/kg peptide NALE (H - Phe - D-Ala Gly - Phe - Leu - Arg - OH) practically neutralizes negative early and remote behavioral consequences of intrauterine hypoxia as well as neonatal emotional-pain stress. Neuroprotective effect is less significantly expressed during introduction of 100 mkg/kg of the peptide G (H - Phe - D-Ala - Gly - Phe - Leu - Gly - OH) from the second to sixth day of life, differing from NALE by replacement of C-ending aminoacid from Arg to Gly. Nitrogen oxide blockade by the accompanying introduction of L-NAME (50mg/kg) hinders the realization of both early (in 7-day-old animals), and remote (in 30-day-old animals) neuroprotective effects of peptide NALE.