The fractional content of water soluble proteins in young and old rats’ brain has been studied. It has been established that the water soluble proteins in the brain of old rats are characterized by the excess of high molecular proteins, as compared to the proteins of young ones. We have supposed that the formation of high molecular proteins as a result of the aggregation of disulfide bonds of low molecular proteins should have been due to the determination of number of sulfhydryl groups. As a result of quantitative determination of sulfhydryl groups, the amount of disulfide bonds in the soluble proteins of the brain in old rats appeared to be 50-60% more, as compared to young rats. It turned out that the activity of NADP-H-dependent disulfide reductase enzyme was about 30-50% less. The impact of biologically active substances, which activate disulfide reductase on the activity of disulfide reductase and the elaboration of conditional avoidance reflex, was specially studied. It has been established that disulfide reductase activity in the various areas of old rats brain on average increases by 50-60-% and relatively the development of conditional avoidance reflexes and the memory is improved by 70%.

Keywords : Water Soluble Proteins, Sulfhydryl and Disulfide Groups, NADP-H-Dependent Enzyme.