MOUSE STRAIN DIFFERENCES IN THE BEHAVIORAL-EFFECTS OF CORTICOTROPIN-RELEASING FACTOR (CRF) AND THE CRF ANTAGONIST ALPHA-HELICAL CRF(9-41)

The effect of the corticotropin-releasing factor (CRF) antagonist cy-h elical CRF(9-41) (alpha H CRF(9-41); 25 and 50 mu g) was examined in f our strains of mice (BALB/C, NIH Swiss, CF-1, and CD) in the elevated plus-maze anxiolytic test and found to significantly increase percent open arm activity in only the BALB/C mice. A marginal anxiolytic respo nse was obtained in NIH Swiss, while no effect of the antagonist was n oted in CF-1 or CD mice in this test. Diazepam (1-4 mg/kg IF) signific antly increased percent open arm activity in all four mouse strains. T hus, all strains were sensitive to the effects of a known anwiolytic i n this test. The locomotor-suppressing effect of the agonist CRF was a ssessed in the four strains of mice. While CRF suppressed locomotor ac tivity in each of the strains, the peptide was more efficacious and mo re potent in the BALB/C strain than in any of the other three strains. The behavioral differences in responsiveness to CRF and the antagonis t alpha H CRF(9-41) could not be explained on the basis of differentia l binding of CRF to forebrain membranes in the four mouse strains. The se data suggest that the BALB/C mouse is more sensitive to the behavio ral effects of CRF and its antagonist than other strains and may be a useful strain for examining the effects of CRF and/or stress.