Basolateral Amygdala Parvalbumin Interneuron Optogenetic Activation Suppresses Anxiety-Like Behavior and Reduces CRF Signaling in Stressed Mice: Circuit Dissection of Fear Inhibition

This study investigates optogenetic activation of basolateral amygdala parvalbumin interneurons suppressing anxiety-like behavior in chronically stressed mice, with characterization of CRF-R1 signaling and downstream projection targets within the context of behavioral neuroscience and fear circuit research, an area of growing scientific importance given its implications for anxiety disorder circuit-based treatment targets, PV interneuron loss as CUS biomarker, and CRF-R1 antagonist combination therapy rationale. Using stereotaxic AAV-DIO-ChR2 injection in PV-Cre mice, 4-week CUS protocol, in vivo optogenetic stimulation (20 Hz, 5ms pulses) during EPM/OFT/NSF, post-hoc immunohistochemistry for c-Fos and CRF-R1, and ex vivo patch clamp of PV-BLA interneurons, we examine PV interneurons providing perisomatic GABAergic inhibition of BLA principal neurons, suppressing CUS-induced hyperexcitability and CRF release; elevated 20-Hz PV activation mimicking normal inhibitory tone lost after chronic stress, restoring anxiety suppression via BLA-prelimbic PFC and BLA-ventral striatum projections in 48 PV-Cre mice: 16 CUS+ChR2 stim, 16 CUS+eYFP sham, 16 no-stress controls; 3 behavioral tests per mouse; ex vivo patch clamp n=24 cells from 6 mice per group drawn from GLNI BSL-1 animal facility with custom fiber optic cannula, Med Associates EPM and OFT arenas, novelty-suppressed feeding (NSF) cage, and Olympus FV1000 confocal for post-hoc histology. Results indicate that PV stimulation during EPM increases open arm time 2.84-fold in CUS mice vs. CUS-eYFP (p<0.001); OFT center time 2.4x; NSF latency reduced 48.4%; CRF-R1 immunoreactivity reduced 38.4% in ChR2 vs. eYFP after stimulation; c-Fos in CRF+ BLA neurons reduced 54.2% (p < 0.001), with 2.84x open arm time; NSF latency -48.4%; CRF-R1 -38.4%; c-Fos CRF+ neurons -54.2% as the primary quantitative benchmark. Concordance between primary and confirmatory measurement approaches exceeded 93%, validating the analytical framework. These findings contribute empirically to behavioral neuroscience and fear circuit research and carry actionable implications for the design of programs and policies targeting anxiety disorder circuit-based treatment targets, PV interneuron loss as CUS biomarker, and CRF-R1 antagonist combination therapy rationale.