As known, food-derived opioid peptides, which include exorphins, hemorphins, casomorphins, are available to influence on behavior and learning ability of newborn mammals. In our experiments were investigated neurotropic effects of rubiscolin-5, which is a opioid fragment of D-ribulose-1,5-bisphosphate carboxylase/oxygenase (RUBISCO). Rat pups of different age had received i/p acute (10 min before experiment) and chronic (1–14 days postnatal) injections of peptide as a model of consuming plant-derived nutrition. Acute administration of peptide exerts reliable anxiolytic effects on 6–7 weeks aged animals (X-maze and forced-swim test); and practically had no influence on learning. Chronic administration of peptide causes much stronger effects. In food-reinforced maze rats of experimental group showed increased number of correct reactions and decreased time of going out from the first compartment. In whole, our results show that rubiscolins are available to modulate the development of pups nervous system and render long-time effects on their behavior. While comparing with effects of casomorphins, rubiscolin-5 demonstrates stronger influence in food-reinforced maze, but causes no effects in pain-reinforced learning. Such distinction may be explained by different affinity of investigated peptides to opioid receptors: rubiscolins mainly bind to delta-sites, while casomorphins seem to be typical mu-agonists. Supported by RBRF, grant No.05-04 -49761.