Heterochronous involvement of neurotrophic factors in the neurochemical organization of learning and memory processes in adult organisms.

Studies were performed on the involvement of neurotrophic factors in the neurochemical mechanisms of the integrative functions of the brain. The effects of various intrahippocampal doses of antibodies to neurotrophic factors--protein S100 and lectin CSL--were studied on the formation, retention, and reproduction of a habituated acoustic startle response and conditioned fear in adult rats. S100b contents in the hippocampus, hypothalamus, frontal cortex, and cerebellar hemispheres and vermis, and in the basal nuclei were measured in rat brains 0.5, 1, 2, 4, 6, 8, 24, and 48 h after long-term habituation to the startle response. Antibodies to neurotrophic factors had selective and dose-dependent effects on the different memory and learning processes underlying these types of behavior. Changes in S100b in brain structures were seen, which were specific in terms of quantitative levels and dynamics, after acquisition of the behavioral habit. The results obtained here, along with previously reported data on the effects of antibodies to S100b and CSL given into the cerebellum, are discussed as experimental support for the hypothesis of the heterochronous neurochemical organization of integrative brain activity.