Corticotropin-Releasing Factor (CRF) Actions on Adenohypophyseal Hormone Secretion by Direct Effects on the Pituitary and by Indirect Effects on the Hypothalamus
The peptidic 41 amino acid corticotropin releasing factor (CRF) is the most important of the CRFs; however, vasopressin is very potent to release adrenocorticotropic hormone and augments the response to CRF. CRF also acts intrahypothalamically to mediate the stress-induced pattern of pituitary hormone release. In addition to the powerful effects at the pituitary level, vasopressin and CRF also have important intrahypothalamic actions which help to bring about the stress-induced pattern of adenohypophyseal hormone secretion. The release of CRF from the hypothalamus is also under the control of several neurotransmitters which include acetylcholine, serotonin, norepinephrine, and Gamma-aminobutyric acid. Although CRF was the first peptide to be postulated to control the release of an anterior pituitary hormone, it was one of the last to be characterized and its structure determined. To determine the intrahypothalamic action of CRF, this peptide was injected into the third ventricle of conscious, freely moving rats and the effect on pituitary hormone release was evaluated.