[Reaction of the hypophysis-adrenal system to dexamethasone as a re flection of adaptive behavior in rats].

In male Wistar rats (180-230 g), adaptive behaviour (the avoidance response, horizontal and vertical activity in open field tests) was compared with the reaction of hypothalamo-pituitary adrenal axis (HPAA) as measured by the corticosterone level in the blood plasma in resting, stress and under the feedback suppression of the HPAA (administration of dexamethasone). The rats with disturbance of adaptive behaviour due to inescapable shock were found to have HPAA feedback inhibition. The basal and stress-induced levels of corticosterone did not differ from the control values in these animals. The adaptive component of behaviour seems to be reflected in the HPAA sensitivity to feedback signals and not to depend on the obviousness of the stress response.