Distinctive Regulation of Emotional Behaviors and Fear-Related Gene Expression Responses in Two Extended Amygdala Subnuclei With Similar Molecular Profiles

Abstract

The central nucleus of the amygdala (CeA) and the lateral division of the bed nucleus of the stria terminalis (BNST) are the two major nuclei of the central extended amygdala that plays essential roles in threat processing, responsible for emotional states such as fear and anxiety. While some studies suggested functional differences between these nuclei, others showed anatomical and neurochemical similarities. Despite their complex subnuclear organization, subnuclei-specific functional impact on behavior and their underlying molecular profiles remain obscure. We here constitutively inhibited neurotransmission of protein kinase C-δ-positive (PKCδ+) neurons—a major cell type of the lateral subdivision of the CeA (CeL) and the oval nucleus of the BNST (BNSTov)—and found striking subnuclei-specific effects on fear- and anxiety-related behaviors, respectively. To obtain molecular clues for this dissociation, we conducted RNA sequencing in subnuclei-targeted micropunch samples. The CeL and the BNSTov displayed similar gene expression profiles at the basal level; however, both displayed differential gene expression when animals were exposed to fear-related stimuli, with a more robust expression change in the CeL. These findings provide novel insights into the molecular makeup and differential engagement of distinct subnuclei of the extended amygdala, critical for regulation of threat processing.

Chronic pain–induced neuronal plasticity in the bed nucleus of the stria terminalis causes maladaptive anxiety

“…Furthermore, Walker et al ( 33 ) reported that intra-CeA injection of anti-CART neutralizing antibodies attenuated yohimbine-induced anxiety-like behavior in the LDB test during alcohol abstinence. Given the anatomical and functional similarities between CeA and BNST ( 32 ), these findings suggest that CART within the BNST may also play a crucial role in the regulation of negative emotions, such as anxiety and fear. Further electrophysiological and behavioral studies are needed to clarify the effects of CART itself, rather than CART-expressing neurons, on the excitability of LH-projecting BNST neurons and anxiety-like behavior.…”

“…PKC-negative neurons are represented by somatostatin-or CRF-positive neurons, and it has been reported that these three cell types cover the majority of CeL neurons and regulate fear and anxiety behaviors (27)(28)(29)(30)(31). A recent study using immunostaining for PKC combined with genetic labeling for CRF or somatostatin neurons showed similar compositions of these three major cell types between the CeL and the ovBNST (32), suggesting that a similar intranuclear reciprocal inhibitory circuit that S1.…”

“…PKCδ-negative neurons are represented by somatostatin- or CRF-positive neurons, and it has been reported that these three cell types cover the majority of CeL neurons and regulate fear and anxiety behaviors ( 27 – 31 ). A recent study using immunostaining for PKCδ combined with genetic labeling for CRF or somatostatin neurons showed similar compositions of these three major cell types between the CeL and the ovBNST ( 32 ), suggesting that a similar intranuclear reciprocal inhibitory circuit that regulates fear/anxiety behaviors also exists in the ovBNST. It was reported that inhibition of PKCδ-positive neurons in the CeL ( 31 ) and the ovBNST ( 32 ) increased the time in open arms in the EPM test, suggesting that PKCδ-positive neurons in these brain regions play a crucial role in anxiety-like behavior.…”

“…A recent study using immunostaining for PKCδ combined with genetic labeling for CRF or somatostatin neurons showed similar compositions of these three major cell types between the CeL and the ovBNST ( 32 ), suggesting that a similar intranuclear reciprocal inhibitory circuit that regulates fear/anxiety behaviors also exists in the ovBNST. It was reported that inhibition of PKCδ-positive neurons in the CeL ( 31 ) and the ovBNST ( 32 ) increased the time in open arms in the EPM test, suggesting that PKCδ-positive neurons in these brain regions play a crucial role in anxiety-like behavior. However, since PKCδ-positive neurons make up a fairly large proportion (35 to 40%) of the ovBNST neurons ( 32 ), it may be necessary to use specific cellular markers expressed in a limited number of ovBNST neurons to determine which population of neurons are involved in the regulation of negative emotions, such as anxiety and fear.…”

“…It was reported that inhibition of PKCδ-positive neurons in the CeL ( 31 ) and the ovBNST ( 32 ) increased the time in open arms in the EPM test, suggesting that PKCδ-positive neurons in these brain regions play a crucial role in anxiety-like behavior. However, since PKCδ-positive neurons make up a fairly large proportion (35 to 40%) of the ovBNST neurons ( 32 ), it may be necessary to use specific cellular markers expressed in a limited number of ovBNST neurons to determine which population of neurons are involved in the regulation of negative emotions, such as anxiety and fear. In this study, we used Cart-Cre mice.…”