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

Matthew B Pomrenze,Robert O Messing,E Zayra Millan,Elena Crawford,Giordano De Guglielmo,Patricia H Janak,Angelo Blasio,Ronald Keiflin,Kenner C Rice,Viktor Kharazia,Olivier George,Jahan Dadgar,Rajani Maiya,F Woodward Hopf

doi:10.3389/fnins.2015.00487

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.

Highlights

Corticotrophin-releasing factor (CRF) is a central regulator of endocrine, autonomic, and behavioral responses to stressors (Koob, 2009)
We found that 94.6 ± 1.2% eYFP+ neurons were immunoreactive for CRF, while 77.1 ± 2.1% of CRF immunoreactive neurons expressed eYFP (Figure 1E; n = 3 rats, 12 amygdala sections/rat)
Until recently our knowledge about the anatomy of CRF systems has rested on traditional neuroanatomical methods and inferences about CRF function through administration of drugs that act at CRF receptors

Summary

Introduction

Corticotrophin-releasing factor (CRF) is a central regulator of endocrine, autonomic, and behavioral responses to stressors (Koob, 2009). CRF cell bodies are distributed in several brain regions, they are concentrated in the central amygdala (CeA), Crh-Cre BAC Transgenic Rat the bed nucleus of the stria terminalis (BNST), and the paraventricular hypothalamic nucleus (PVN; Wang et al, 2011). For CeL CRF neurons in particular, tract-tracing studies have identified CRF projections from the rat CeA to the locus coeruleus (Van Bockstaele et al, 1998; Reyes et al, 2011), parabrachial nuclei (Moga and Gray, 1985), the midbrain central gray (Gray and Magnuson, 1992), the dorsal vagal complex [including the nucleus tractus solitarius (NTS)] (Gray and Magnuson, 1987), the pontine reticular nucleus (Fendt et al, 1997), the mesencephalic trigeminal nucleus (Sakanaka et al, 1986), and the BNST (Sakanaka et al, 1986). Several recent studies have helped clarify CRF architectures and functions using Crh-Cre mouse lines (Gafford et al, 2012, 2014; Wamsteeker Cusulin et al, 2013; McCall et al, 2015), but thorough characterization of CRF circuits across brain structures, and across species, is still lacking

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Conclusion