Acute effects of alprazolam and adinazolam on the concentrations of corticotropin-releasing factor in the rat brain.

Corticotropin-releasing factor (CRF) is the major physiological regulator of the hypothalamic-pituitary-adrenal (HPA) axis. However, considerable evidence indicates that CRF may be responsible for integrating not only the endocrine, but the autonomic and behavioral responses of an organism to stress as well. In addition, clinical studies indicate that CRF of both hypothalamic and extrahypothalamic origin may be hypersecreted in major depression as well as other psychiatric disorders. These findings, taken together, led to the hypothesis that the efficacy of antidepressant and/or anxiolytic drugs may be related to their actions on CRF-containing neural pathways in the central nervous system (CNS). Therefore, alterations of CRF concentrations in 18 rat brain regions were studied after acute administration of a tricyclic antidepressant (imipramine) or one of two triazolobenzodiazepines (alprazolam or adinazolam) that possess anxiolytic properties typical of benzodiazepines, as well as purported antidepressant activity unique to these compounds. Treatment with alprazolam or adinazolam increased hypothalamic CRF concentrations, which was associated with lower plasma ACTH concentrations. In contrast, the concentration of CRF was markedly reduced in the locus coeruleus, amygdala, and several cortical regions by either triazalobenzodiazepine. Acute treatment with imipramine was without effect on CRF concentrations in any brain region studied. Of particular interest is the finding that the two triazolobenzodiazepines exert effects on CRF concentrations in the locus coeruleus and hypothalamus that are opposite to CRF changes seen after stress.