CHARACTERISTICS OF FAST FEEDBACK CONTROL OF CORTICOTROPHIN RELEASE BY CORTICOSTEROIDS

Abstract

SUMMARY Corticosterone was administered intraperitoneally to rats, and the consequent changes in plasma corticosterone concentration traced. Stress (sham bilateral adrenalectomy) was applied at various times when the plasma corticosterone concentration was changing at different rates, and it was shown that there was a critical rate of rise of plasma corticosterone concentration of about 1·3 μg/100 ml plasma/min in excess of which the stress response was inhibited. Rates of rise less than this did not affect the stress response. A state of ' saturation' of the control system was also demonstrated to result from high plasma corticosterone concentrations when the response to stress was not inhibited as above. A model of the system is suggested to explain these and other data.