Fig. 4.

Chemogenetic inhibition of BNST^CRHneurons enhances innate fear response evoked by cat odor. (A) Illustration of experimental settings and representative trajectory plots of individual mice exposed to clean or soiled cat litter. (B) Assessment of the behavioral profile of mice exposed to cat odor. Cat odor exposure significantly decreased locomotor activity and increased freezing behavior (n = 16–19/group), without altering approaches, rearing, or mean distance from the odor zone. (C) Illustration of experimental settings and representative trajectory plots of individual cat odor exposed mice expressing control fluorophore or hM4Di receptors. (D) Inhibition of BNST^CRH neurons resulted in enhanced fear response indicated by all behavioral variables (n = 8–10/group). (E) Representative confocal microscopic images of the BNST from cat odor exposed mice expressing control fluorophore or hM4Di receptors (40 min after CNO injection). (F) hM4Di-expressing neurons exhibited reduced neuronal activity during cat odor exposure compared to controls indicated by decreased cFos+/mCherry + co-labeling (n = 6–8/group). (G) Inhibition of BNST^SST neurons had no impact on the fear response indicated by all behavioral variables (n = 8–9/group). Data are expressed as means ± SEM. *p < 0.05, **p < 0.01, #p = 0.08 (Student t-test).