Morphofunctional Organization of the Connections From the Medial and Intermediate Parts of the Central Nucleus of the Amygdala Into Distinct Divisions of the Lateral Hypothalamic Area in the Rat

Abstract

Projections from the central nucleus of the amygdala (CEA) into the lateral hypothalamic area (LHA) show a very complex pattern. After injection of an anterograde tracer (Phaseolus vulgaris leucoagglutinin—PHAL) into the medial and intermediate parts of the CEA, we observed that labeled axons converged onto the caudal lateral LHA but provided distinct patterns in rostral tuberal regions. These projections were compared to that of neurons containing the peptides “melanin-concentrating hormone” (MCH) or hypocretin (Hcrt). Because the distribution of these neurons is stereotyped, it was possible to characterize distinct divisions into the LHA. Some of them in the rostral tuberal LHA [the dorsal (LHAd) and suprafornical regions (LHAs)] received a distinct innervation by projections that originated from neurons in respectively anterior or posterior regions of the medial part (CEAm) or from the intermediate part (CEAi) of the central nucleus. Therefore, this work illustrates that projections from the CEAm and CEAi converge into the caudal lateral LHA but diverge into the rostral tuberal LHA.

Central Amygdala Projections to Lateral Hypothalamus Mediate Avoidance Behavior in Rats

“…The topography of CeA-LH projections provides information on the potential phenotypes of CeA and LH cells participating in this circuitry. Here, we report that a majority of CeA-LH projections originate from the CeM, as indicated by retrograde tracing using Retrobeads, consistent with previous findings in Long-Evans (Reppucci and Petrovich, 2016) and Sprague Dawley rats (Barbier et al, 2018). The CeL contains a high density of CRFexpressing cells that release CRF both locally and distally (Pomrenze et al, 2015), whereas the CeM contains a high density of CRFR1-expressing cells that can be activated by CRF (Radulovic et al, 1998).…”

“…Using an mCherry-expressing AAV5 anterograde tracer, we report that CeA cells mostly project to the rostrodorsal LH, in agreement with a study by Reppucci and Petrovich (2016) in rats. In addition, Barbier et al (2018) showed that cells from caudal CeM project to this region of LH in rats. The rostrodorsal LH is a heterogeneous area but contains a relatively high density of Hcrt1 cells in rats (Barbier et al, 2018), and LH Hcrt1 cells have been implicated in avoidance behavior in mice (Giardino et al, 2018).…”

“…In addition, Barbier et al (2018) showed that cells from caudal CeM project to this region of LH in rats. The rostrodorsal LH is a heterogeneous area but contains a relatively high density of Hcrt1 cells in rats (Barbier et al, 2018), and LH Hcrt1 cells have been implicated in avoidance behavior in mice (Giardino et al, 2018). Indeed, previous work in mice showed that CeA projections innervate LH Hcrt1 cells (Nakamura et al, 2009), supporting the idea that CeA cells may drive avoidance via modulation of LH Hcrt1 cell activity.…”

Projections from the dorsomedial division of the bed nucleus of the stria terminalis to hypothalamic nuclei in the mouse

“…The mouse monoclonal ORX antibody (Angio‐Proteomie, Cat# hAP‐0500, ABIN1983384) was produced from a hybridoma (mouse myeloma fused with spleen cells from a mouse immunized with a peptide, aa 35‐65, O43612) from human Orexin‐A protein. The immunohistochemistry produced a pattern of staining similar to that described elsewhere in the literature (Barbier et al, 2018).…”

Amygdala substructure volumes in Major Depressive Disorder

“…Deeper substructural analysis investigating the constituent parts of the amygdala, i.e., the nine amygdalar nuclei and three composite clusters (laterobasal, centromedial and superficial groups), demonstrated a clear increase in the right medial nuclei volumes in MDD ( Table 2 ). The centromedial group consists of the principal output nuclei to the hypothalamus ( Barbier et al, 2018 , Van de Kar and Blair, 1999 ) and have been shown to be particularly sensitive to negative emotional stimuli in HC ( Hrybouski et al, 2016 ).…”