Time course of hypothalamic CRF activity after the administration of two different stresses

The time course of hypothalamic corticotropin-releasing factor (CRF) activity after the administration of ether stress was different from that after immobilization stress. The maximal response CRF activity was observed 2 min after ether stress, followed by a precipitous decrease 5 min after the stress. A gradual increase of CRF activity was subsequently observed for several minutes with fluctuated changes. Thus, response pattern was vibratory. But under immobilization stress, markedly fluctuant changes of CRF activity seen in the case of ether stress did not appear after the maximal response observed at 2 min, indicating that the response pattern was not vibratory. On the other hand, the concentration of plasma corticosterone increased significantly 5 min after the ether or immobilization stress with the peak value around 17 min.