Somatostatin neurons of the bed nucleus of stria terminalis enhance associative fear memory consolidation in mice

Bruzsik, Bíborka and Bíró, László and Zelena, Dóra and Bodóné Sipos, Eszter and Szebik, Huba and Farkas, Imre and Csillag, Veronika and Finszter, Cintia Klaudia and Mikics, Éva and Tóth, Máté (2021) Somatostatin neurons of the bed nucleus of stria terminalis enhance associative fear memory consolidation in mice. JOURNAL OF NEUROSCIENCE, 41 (9). pp. 1982-1995. ISSN 0270-6474

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Abstract

Excessive fear learning and generalized, extinction-resistant fear memories are core symptoms of anxiety and trauma-related disorders. Despite significant evidence from clinical studies reporting hyperactivity of the bed nucleus of stria terminalis (BNST) under these conditions, the role of BNST in fear learning and expression is still not clarified. Here, we tested how BNST modulates fear learning in male mice using a chemogenetic approach. Activation of GABAergic neurons of BNST during fear conditioning or memory consolidation resulted in enhanced cue-related fear recall. Importantly, BNST activation had no acute impact on fear expression during conditioning or recalls, but it enhanced cue-related fear recall subsequently, potentially via altered activity of downstream regions. Enhanced fear memory consolidation could be replicated by selectively activating somatostatin (SOM), but not corticotropin- releasing factor (CRF) neurons of the BNST, which was accompanied by increased fear generalization. Our findings suggest the significant modulation of fear memory strength by specific circuits of the BNST.SIGNIFICANCE STATEMENT:The bed nucleus of stria terminalis mediates different defensive behaviors and its connections implicate its integrative modulatory role in fear memory formation, however, the involvement of BNST in fear learning has yet to be elucidated in detail. Our data highlight that BNST stimulation enhances fear memory formation without direct effects on fear expression. Our study identified somatostatin cells within the extended amygdala as specific neurons promoting fear memory formation. These data underline the importance of anxiety circuits in maladaptive fear memory formation, indicating elevated BNST activity as a potential vulnerability factor to anxiety and trauma-related disorders.

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