A Transgenic Rat for Investigating the Anatomy and Function of Corticotrophin Releasing Factor Circuits

Abstract

Corticotrophin-releasing factor (CRF) is a 41 amino acid neuropeptide that coordinates adaptive responses to stress. CRF projections from neurons in the central nucleus of the amygdala (CeA) to the brainstem are of particular interest for their role in motivated behavior. To directly examine the anatomy and function of CRF neurons, we generated a BAC transgenic Crh-Cre rat in which bacterial Cre recombinase is expressed from the Crh promoter. Using Cre-dependent reporters, we found that Cre expressing neurons in these rats are immunoreactive for CRF and are clustered in the lateral CeA (CeL) and the oval nucleus of the BNST. We detected major projections from CeA CRF neurons to parabrachial nuclei and the locus coeruleus, dorsal and ventral BNST, and more minor projections to lateral portions of the substantia nigra, ventral tegmental area, and lateral hypothalamus. Optogenetic stimulation of CeA CRF neurons evoked GABA-ergic responses in 11% of non-CRF neurons in the medial CeA (CeM) and 44% of non-CRF neurons in the CeL. Chemogenetic stimulation of CeA CRF neurons induced Fos in a similar proportion of non-CRF CeM neurons but a smaller proportion of non-CRF CeL neurons. The CRF1 receptor antagonist R121919 reduced this Fos induction by two-thirds in these regions. These results indicate that CeL CRF neurons provide both local inhibitory GABA and excitatory CRF signals to other CeA neurons, and demonstrate the value of the Crh-Cre rat as a tool for studying circuit function and physiology of CRF neurons.

Basolateral to Central Amygdala Neural Circuits for Appetitive Behaviors

“…Cell-type specific studies have shown evidence for the involvement of several genetically defined CeA neurons in aversive behaviors such as defensive responses and anxiogenesis (Andero et al, 2014; Han et al, 2015; Haubensak et al, 2010; Isosaka et al, 2015; Li et al, 2013; McCall et al, 2015; Pomrenze et al, 2015; Sanford et al, 2017). However, despite early evidence suggesting the involvement of the CeA in appetitive behaviors (Galaverna et al, 1993; Gallagher et al, 1990; Parkinson et al, 2000; Ritter and Hutton, 1995) and more recent activation studies demonstrating a modulatory role of the CeA in appetitive behaviors (Cai et al, 2014; Robinson et al, 2014; Seo et al, 2016), how appetitive behavior integrates into a structural and functional model of amygdala has yet to be established.…”

The Corticotropin Releasing Factor Receptor 1 in Alcohol Use Disorder: Still a Valid Drug Target?

“…This also appears to involve an interaction with CRF, since anxiety produced by CRF injections into the lateral ventricles was absent in prodynorphin knockout mice or in mice pretreated with norBNI (Bruchas et al, 2009, Land et al, 2008). Supporting an interaction between CRF and dynorphin, roughly 60–75% of CRF neurons in the rat and mouse CeA co-express dynorphin (Marchant et al, 2007, Kim et al, 2017, Pomrenze et al, 2015). Nothing is known about this interaction in primates.…”

“…Both species contain many CRF neurons in the paraventricular hypothalamus (PVN), CeA, and bed nucleus of the stria terminalis (BNST), but extended amygdala CRF neurons exhibit anatomical differences. CRF neurons in mouse CeA are found anteriorly, whereas in rat they cluster in the posterior portion of the CeA (Asan et al, 2005, Pomrenze et al, 2015, Sanford et al, 2017). The lateral capsular subregion of the CeA, which contains serotonergic inputs in both species, has a dense CRF fiber plexus in mice that is absent in rats, providing an anatomical basis for interspecies differences in CRF-serotonergic interactions in the CeA (Asan et al, 2005).…”

“…The lateral capsular subregion of the CeA, which contains serotonergic inputs in both species, has a dense CRF fiber plexus in mice that is absent in rats, providing an anatomical basis for interspecies differences in CRF-serotonergic interactions in the CeA (Asan et al, 2005). In addition, CRF neurons in the mouse dorsal BNST are widely distributed and lie outside of the oval nucleus, whereas in rat they cluster in the oval nucleus (Nguyen et al, 2016, Pomrenze et al, 2015). Adding to the anatomical differences, there is evidence that BNST CRF neurons have different morphological and electrophysiological properties when compared in rat, mouse, and non-human primates (Daniel et al., 2017).…”

Localization of the delta opioid receptor and corticotropin-releasing factor in the amygdalar complex: role in anxiety

“…Additionally, the ventromedial nucleus of the hypothalamus and the pontine parabrachial nucleus provide moderate enkephalinergic afferents to the CeA (Poulin et al, 2006). Intrinsic amygdalar enkephalinergic neurons, that are known to be distinct from amygdalar CRF neurons (Drolet et al, 2001; Reyes et al, 2008; Van Bockstaele et al, 2010; Reyes et al, 2011; Andero et al, 2013; Kravets et al, 2015), may play a role in the local circuit regulation of amygdalar neurons as there exists significant evidence describing such intrinsic connections in the CeA (Haubensak et al, 2010; Ciocci et al, 2010; Pomrenze et al, 2015). Potential opioidergic afferents to the BLA could also originate from local axonal arborizations of intrinsic enkephalinergic pyramidal neurons originating from the BLA (McDonald et al, 2005; Pitkanen et al, 2003).…”