[Dependence of long-lasting effects of the ACTH(4-10) analogue semax on the time of its neonatal administration].

Long-lasting behavioural effects of chronic administration of synthetic ACT(4-10) analogue Semax (MEHFPGP) during early neonatal life were studied. The peptide was injected daily intraperitoneally in dose 0.05 mg/kg during the first, second or second-third weeks of postnatal development. It was shown that the peptide injections during the first week lead to a decrease and during second or second-third weeks--to an increase of exploratory activity in 4-8-week aged rats. Furthermore, the peptide adminictration at all times diminished anxiety and improved learning ability of adult rats. The data obtained show that Semax neonatal administration during the first three weeks of life modulates development of brain structures involved in regulation of exploration, anxiety and learning.