Regulation of corticotropin-releasing factor (CRF) messenger ribonucleic acid and CRF peptide in the amygdala: studies in primary amygdalar cultures.

Amygdalar CRF has been implicated in the mediation of stress behaviors. The signal transduction pathways that regulate amygdalar CRF are not well understood. In this report, we have examined the effect of protein kinase A and C activators, dexamethasone, and interleukin 6 on CRF messenger RNA (mRNA) and CRF peptide expression in dissociated amygdalar cultures. The amygdala from E19 rat pups was dissected out bilaterally and dissociated in 0.25% trypsin for 10-15 min and plated. On day 17 in culture, CRF mRNA and peptide were measured following treatment with the following agents: forskolin, the phorbol ester-phorbol 12 myristate 13-acetate (TPA), dexamethasone, and interleukin-6 (IL6). Both forskolin and IL6, but not TPA, increased CRF mRNA in a time- and dose-dependent manner. Secretion and intracellular content of the CRF peptide also increased with both forskolin and IL6 treatment but not with TPA. Dexamethasone treatment did not alter the expression of CRF message or peptide. Transfection of the primary cultures with a rat CRF promoter-luciferase reporter construct followed by treatment with all four agents produced alterations in luciferase expression that were consistent with changes observed at the level of CRF mRNA and peptide. The results suggest that CRF regulation in the amygdala differs from that known to occur in the hypothalamus, and that elevation of IL6 levels within the central nervous system may directly act to stimulate CRF production and secretion from limbic structures such as the amygdala, to promote subsequent behavioral changes.