Role of neurotrophic factors in adaptational processes of the nervous system.

Neurotrophic factors (NTF) are low-molecular-weight proteins which epigenetically determine neuron survival during embryogenesis and the maintenance of their morphofunctional properties in the adult organism. NTF are located in mesenchymal tissues and reach neuron bodies by means of retrograde axoplasmic transport in nerve fibers; in cell bodies, NTF increase anabolic activity, neurotransmitter synthesis, and structural protein production. Neuron cell bodies have two types of specialized receptors for binding the most common NTF, nerve growth factor (NGF). In the brain, NGF does not affect adrenergic neurons, as it does in the periphery, but acts on cholinergic neurons in the basal part of the forebrain. The forebrain plays the major role in the processes of learning, memory, and plasticity, i.e., in the entire complex of adaptational responses of the nervous system, and these may thus depend on the biological activities of substances, including NTF, in forebrain tissues. An experimental model was developed consisting of organotypic co-cultivation of rat hippocampus fragments with chick embryo dorsal root ganglia. This model was used to demonstrate that epileptiform activity in the hippocampus is associated with increases in NTF release, which can be regarded as an adaptive compensatory response to nerve cell damage occurring during convulsive activity.