Figure 2.
Chemogenetic activation of the BNST facilitates fear learning, but not fear recall. A, Schematics of virus injections in vgat-ires-cre mice and representative photomicrograph of mCherry expression. Right panels show minimum (filled areas) and maximum (areas with colored outlines) extensions of mCherry expression in the BNST. B, Patch clamp recordings from BNST slices: representative photomicrograph depicting a vGAT+ neuron filled with biocytin. Right panel shows representative trace of a hM3Dq expressing neuron indicating CNO-mediated depolarization in the presence of TTX, which was absent in BNSTvGAT neurons expressing control fluorophore. C, CNO administration also elevated the frequency of APs evoked by depolarizing current steps and decreased the rheobase. D, Intraperitoneal injection of CNO under homecage condition induced significant c-Fos expression in hM3Dq-mCherry-expressing neurons (control: n = 9, hM3Dq: n = 9). E, Experimental design for auditory fear conditioning. F, I, Schematics of chemogenetic modulation of the BNST during fear conditioning or memory consolidation, respectively, and freezing behavior exhibited during conditioning. BNST stimulation did not affect acute fear response (freezing) during conditioning. G, BNST stimulation during conditioning did not affect contextual fear recall, but enhanced cued fear recall (H; control: n = 8, hM3Dq: n = 9). Similarly, chemogenetic activation of BNSTvGAT neurons during fear memory consolidation resulted in enhanced cued fear recall with additional fear generalization on day 2 (freezing during baseline; K), without altering contextual fear recall in context A (J). L, Experimental design for chemogenetic activation of the BNST during cued fear recall with conditioned (CS+) and safety cue (CS–) presentations. Freezing response of hM3Dq and control groups were similar during all testing phase, i.e., conditioning (M), short CS+ and CS– recall (N), CS+ and CS– induced fear recall (O; control: n = 8, hM3Dq: n = 13). On freezing time curves, each major tick depicts two to three footshock (FS) blocks in case of conditioning, and a 180-s block, starting with a 150-s pretone baseline period (BL) in case of recall test. All data are represented as mean ± SEM. Asterisks represent main effect of one-way, two-way, or repeated-measure ANOVA: *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001; # represents significant difference in BL period p < 0.05.