[Characteristics of free-radical oxidation and antiradical protection of the brain in adaptation to chronic stress].

During the phase of long-lasting adaptation to chronic emotional painful stress three stages have been distinguished on the basis of physiological and neurobiochemical data. The first stage (1 week of stress)--transition from urgent to long-lasting adaptation--corresponds to labilization of vegetative indices, predominance of fear reactions and suppression of research behaviour in rats, inhibition of lipid peroxidation, activation of superoxide scavenging activity, decrease in cholesterol content in brain lipids. The second stage (2 weeks of stress)--long-lasting adaptation--is characterized by normalization of the behaviour, stabilization of high blood pressure, maximum brain antiradical activity and low level of lipid peroxidation. The third stage (3 weeks of stress)--transition from long-lasting adaptation to exhaustion--is characterized by blood pressure lowering, disturbed regulation of vegetative functions, behavioural hyperactivity in the open field, increased lipid peroxidation and decreased phospholipid content.