Corticotropin-Releasing Hormone Signaling in the Oval Bed Nucleus of the Stria Terminalis Mediates Chronic Stress-Induced Negative Valence Behaviors Associated with Anxiety

Abstract

The bed nucleus of stria terminalis (BNST) is a forebrain region highly sensitive to stress that expresses corticotropin-releasing hormone (CRH) neuropeptide at high levels and regulates negative valence behaviors associated with anxiety. However, how chronic stress modulates CRH signaling and neuronal activity in BNST remains unknown. We subjected C57BL6/J mice to a 6-week chronic variable mild stress (CVMS) paradigm and investigated the effects on behavior, BNST cellular neurophysiology, and BNST CRH signaling. We also utilized pharmacological infusions and optogenetics to decipher and mimic the effects of CVMS on BNST cellular neurophysiology and behavior. CVMS elevated plasma corticosterone levels, induced negative valence behaviors associated with anxiety, diminished M-currents (voltage-gated K+currents that stabilize membrane potential and regulate neuronal excitability), and increased mEPSC amplitude in ovBNST. Additionally, the number of c-fos+, CRH+, and CRH activator pituitary adenylate cyclase-activating polypeptide (PACAP)+cells were increased while CRH inhibitor striatal-enriched protein tyrosine phosphatase (STEP)+cells were decreased in ovBNST. These expression data were confirmed with qPCR. CVMS also activated PKA in BNST and the electrophysiological and behavioral effects of CVMS were reversed by ovBNST infusion of the PKA-selective antagonist H89. Moreover, optogenetic activation of ovBNST directly induced negative valence behaviors associated with anxiety, mimicking the effects of CVMS. CVMS mediates effects on negative valence behaviors associated with anxiety by activating CRH signaling components and cellular excitability in ovBNST Our findings decipher an important CRH-associated stress molecular signature in BNST and advance our understanding of the neural circuitry underlying stress-induced disorders.

Crh receptor priming in the bed nucleus of the stria terminalis (BNST) induces tph2 gene expression in the dorsomedial dorsal raphe nucleus and chronic anxiety

“…Recent studies by Ren and colleagues (2018) have demonstrated that BNST projection neurons preferentially innervate DR serotonergic neurons projecting to the central nucleus of the amygdala (DR SERT →CeA neurons) that in turn increase anxiety-like defensive behavioral responses, a finding consistent with previous retrograde tracing from the dorsomedial DR (Peyron et al, 1998). Although not discussed by Ren and colleagues (2018), the BNST neurons projecting to DR SERT →CeA neurons (located in the dorsomedial DR) are almost exclusively located in the oval nucleus of the BNST (BSTLD), the location of a dense population of Crh-expressing neurons in rats and mice (Hu et al, 2019;Nguyen et al, 2016;Dabrowska et al, 2016). Furthermore, using injections of a'floxed' anterograde tracer (rAAV5/EF1a-DIO-mCherry) into the oval nucleus of the BNST of CRFp3.0CreGFP transgenic mice and analogous methods in rats, Dabrowska and colleagues showed that CRF neurons in the oval BNST selectively target the DRD, also referred to as the dorsomedial DR (Dabrowska et al, 2016), i.e., the same region where we observed changes in Tph2 mRNA expression in our study.…”

“…Conversely, serotonergic projections from the DR to BNST Crh-expressing neurons, through activation of 5-HT 2C receptors, promote development of an anxiety-like state (Marcinkiewcz et al, 2016). Finally, direct activation of Crh neurons in the oval BNST nucleus induces an anxiety-like state that mimics that observed following chronic stress (Hu et al, 2019). Thus, Crh-expressing neurons in the oval subnucleus of the BNST and serotonergic neurons within the dorsomedial DR appear to have reciprocal connections that play a role in control of emotional behavior, including anxiety-like defensive behavioral responses.…”

Chronic stress-induced synaptic changes to corticotropin-releasing factor-signaling in the bed nucleus of the stria terminalis

“…Importantly, early life stress and CVMS paradigms result in increased CRF and PKA expression in the BNST (Hu et al, 2020a,b). PKA antagonism ameliorates the effects of CVMS on avoidance behaviors (Hu et al, 2020a). Taken together, evidence suggests that PKA is important for Proposed mechanism of stress-induced neuroplasticity in the anterodorsolateral BNST.…”

“…CRF infusion directly into the BNST also increases avoidance behaviors (Sahuque et al, 2006). More recent studies using circuit-level approaches to modulate specific BNST cell populations show that most BNST neurons, including the CRF+ population, increase avoidance behaviors when activated (Kim et al, 2013;Gungor and Pare, 2016;Marcinkiewcz et al, 2016;Giardino et al, 2018;Giardino et al, 2018;Yamamoto et al, 2018;Hu et al, 2020a). Optogenetic activation of neurons expressing dopamine receptor 1 (Drd1), which is reported to colocalize with CRF in ovBNST neurons, increases avoidance in open field and elevated plus maze (EPM) tests (Kim et al, 2013;Hu et al, 2020a) and increases respiration, a physiological sign of stress (Kim et al, 2013).…”

“…Therefore, conclusions from Ventura-Silva et al suggest stress decreases CRF-signaling sensitivity. Several studies provide evidence for this theory; CRFR1 antagonism in the BNST reliably blocks the behavioral effects of CRF infusion (Sahuque et al, 2006) and chronic (Hu et al, 2020a) and early life stress (Hu et al, 2020a,b), while CRFR2 antagonism does not block CRF-infusion induced avoidance behavior in the EPM (Sahuque et al, 2006). In fact, CRFR2-deficient mice demonstrate increased avoidance behavior (Bale et al, 2000).…”