Regulation of Rat Hypothalamic Corticotropin-Releasing Hormone Secretion in vitro: Potential Clinical Implications

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Abstract
Corticotropin-releasing hormone (CRH) is located in both the hypothalamus (1) and several extrahypothalamic brain regions (2). Different reports suggest that CRH not only stimulates pituitary adrenocorticotropin (ACTH) secretion (3), but also activates the sympathetic nervous system (4) and causes behavioral changes (5–10). Behavioral studies conducted primarily in rats have indicated that CRH administered intracerebroventricularly (icv) causes anxiety-like behaviors. Such behaviors are, in part, influenced by the animal’s familiarity with the environment. In single-caged rats, tested in a familiar environment, CRH increases locomotion, rearing, and self-grooming (10) and decreases food intake (5,8). On the other hand, CRH administered to rats in a novel environment decreases locomotion, rearing, and food intake and increases self-grooming (10). In addition, icv CRH administration increases aggression and mounting behavior of male rats (10). In contrast, microinfusion of CRH into the arcuate hypothalamic nucleus and mesencephalic central gray area of estrogen-primed female rats causes decreased sexual receptivity (9). These effects of CRH are compatible with the concept that this peptide may be an important integrative factor that coordinates endocrine, autonomic, and behavioral responses to stress.