Patterns of the functioning of the hypophyseoadrenocortical system in the presence of repeated stressful stimulations.

The relationship of the magnitude of the response of the hypophyseoadrenocortical system (HACS) to the strength of the stimulus in the presence of isolated or repeated stressor influences was determined in experiments on awake rats. Electrical stimulation of 0.1-0.9 mA of the skin of the paws for 3 min served as the stimulus. The reaction of HACS was judged on the basis of the determination of blood corticosteroids. Changes take place in the physiological characteristics of the system 30 mins after the termination of the stressor activation of the HACS. These changes do not depend on the strength of the initial stressor, and consist of a decrease in the threshold of excitability and a reduction in the maximum of the reaction to stressors of greater strength. The reaction to repeated stimulation at small strengths of the initial stressor proved to be larger or equal to the response of the system to the initial stimulation. At greater strengths of the stressor the reaction to repeated stimulation is significantly less than to the initial stimulation.