Stress mediated changes in hypothalamic corticotropin releasing factor-like immunoreactivity.

Hypothalamic corticotropin releasing factor-like immunoreactivity (CRF-LI), plasma ACTH and corticosterone levels were measured by radioimmunoassay over a two hour period of restraint stress. The results of this study demonstrate a significant decrease in hypothalamic CRF-LI levels 15 and 30 minutes after the start of restraint stress which is followed by a significant increase at 60 minutes that is abolished by cycloheximide pretreatment. Plasma ACTH and corticosterone levels were significantly elevated after 15, 30, 60, 90, and 120 minutes of restraint stress. These results are consistent with a release of CRF from the hypothalamus during stress. The cycloheximide-sensitive increase in hypothalamic CRF-LI indicates that synthesis of CRF-41 occurs during prolonged stress. These results suggest that the response of an organism to exposure to a long-term, high intensity stress involves both the release and synthesis of CRF-41.