Molecular, Morphological, and Functional Characterization of Corticotropin-Releasing Factor Receptor 1-Expressing Neurons in the Central Nucleus of the Amygdala

The central nucleus of the amygdala (CeA) is a brain region implicated in anxiety, stress-related disorders and the reinforcing effects of drugs of abuse. Corticotropin-releasing factor (CRF, Crh) acting at cognate type 1 receptors (CRF(1), Crhr1) modulates inhibitory and excitatory synaptic transmission in the CeA. Here, we used CRF(1):GFP reporter mice to characterize the morphological, neurochemical and electrophysiological properties of CRF(1)-expressing (CRF(1)+) and CRF(1)-non-expressing (CRF(1)–) neurons in the CeA. We assessed these two neuronal populations for distinctions in the expression of GABAergic subpopulation markers and neuropeptides, dendritic spine density and morphology, and excitatory transmission. We observed that CeA CRF(1)+ neurons are GABAergic but do not segregate with calbindin (CB), calretinin (CR), parvalbumin (PV), or protein kinase C-δ (PKCδ). Among the neuropeptides analyzed, Penk and Sst had the highest percentage of co-expression with Crhr1 in both the medial and lateral CeA subdivisions. Additionally, CeA CRF(1)+ neurons had a lower density of dendritic spines, which was offset by a higher proportion of mature spines compared to neighboring CRF(1)– neurons. Accordingly, there was no difference in basal spontaneous glutamatergic transmission between the two populations. Application of CRF increased overall vesicular glutamate release onto both CRF(1)+ and CRF(1)– neurons and does not affect amplitude or kinetics of EPSCs in either population. These novel data highlight important differences in the neurochemical make-up and morphology of CRF(1)+ compared to CRF(1)– neurons, which may have important implications for the transduction of CRF signaling in the CeA.