The NMDA-NR1 receptor subunit and the mu-opioid receptor are expressed in somatodendritic compartments of central nucleus of the amygdala neurons projecting to the bed nucleus of the stria terminalis

Abstract

The pathway between the central nucleus of the amygdala (CeA) and the bed nucleus of the stria terminalis (BNST) is emerging as a critical mediator of stress-related affective processes. Evidence also indicates that exposure to drugs of abuse, like opioids, is associated with NMDA-type glutamate receptor-dependent plasticity in the CeA and BNST. However, there is little evidence that NMDA receptors are expressed in CeA neurons projecting to the BNST, or are required for opioid-induced BNST neural activation. Immunoelectron microscopy, tract tracing, and conditional gene deletion technology were used to investigate the synaptic organization of the NMDA receptor and the mu-opioid receptor (μOR) in the CeA-BNST pathway. By dual labeling electron microscopy, numerous CeA-BNST projection neurons expressed the NMDA-NR1 receptor subunit (NR1) or μOR. By triple labeling, it was also found that NR1 and μOR were co-expressed in some CeA-BNST projection neurons. Despite being colocalized in somato-dendritic compartments of CeA neurons, NR1 and μOR were rarely expressed in their axonal terminations in the BNST. Deleting the NR1 gene in CeA neurons resulted in a reduction of morphine-induced Fos protein labeling in the ventral BNST. In summary, NR1 and μOR are coexpressed in somatodendritic sites of CeA neurons, including those projecting to the BNST. In addition, expression of the NR1 gene in CeA neurons is required for morphine-induced BNST neural activation. Thus, postsynaptic NMDA receptors and μORs are positioned for the co-modulation of CeA projection neurons to the BNST, which may provide a synaptic substrate for stress-induced emotional processes critically involved in opioid addictive behaviors.

Corticotropin-releasing factor in the mouse central nucleus of the amygdala: Ultrastructural distribution in NMDA-NR1 receptor subunit expressing neurons as well as projection neurons to the bed nucleus of the stria terminalis

“…In the present study, the general pattern of CRF, as well retrograde labeling, in the mouse was found to be in agreement with prior studies in this species (Beckerman and Glass 2012; Treweek et al 2009), and in the rat as well (Cassell and Gray 1989; Jaferi and Pickel 2009; Justice et al 2008; Treweek et al 2009). These broad anatomical similarities correspond to generally similar responses of the CeA CRF system to relevant behaviors, including exposure to, or withdrawal from, drugs of abuse (McNally and Akil 2002; Nie et al 2004; Roberto et al 2010; Shaw-Lutchman et al 2002), in addition to conditioned fear behaviors (Kolber et al 2008; Thompson et al 2004).…”

“…Somata of CeA neurons expressing labeling for FG and CRF contained large nuclei and a dense endomembrane system, both cytological features similar to CeA-BNST projection neurons that express NR1 and mu-opioid receptor as previously shown by triple labeling immunocytochemistry (Beckerman and Glass 2012). In addition to co-expression in somata and dendrites, both single FG labeled, and dual FG and CRF labeled somata and dendrites were contacted by CRF expressing axon terminals.…”

“…Tracers were administered as previously described (Beckerman and Glass 2012). Under deep isoflurane anesthesia, either fluorogold (FG [Fluorochrome, Denver, CO], 2% in phosphate buffer [PB]) or BDA ([Invitrogen, Carlsbad, CA]; 10% in PB) were unilaterally microinjected in the BNST or CeA, respectively.…”

“…This pathway is implicated in neurobehavioral responses to stress (Jasnow et al 2004), as well as stress-induced reinstatement of drug self-administration (Erb et al 2001), processes that critically involve NMDA receptor activation. Although it has been shown that NMDA receptors are prominently expressed in CeA neurons that project to the BNST (Beckerman and Glass, 2012), aside from previous indirect light microscopic approaches (Sakanaka et al 1986), there is no direct ultrastructural data characterizing the expression of CRF in somata and dendrites of CeA-BNST projection neurons, as well as CRF expressing axons that contact them.…”

Redistribution of NMDA Receptors in Estrogen-Receptor-β-Containing Paraventricular Hypothalamic Neurons following Slow-Pressor Angiotensin II Hypertension in Female Mice with Accelerated Ovarian Failure

“…Reduced labeling for this antiserum has been shown following rAAV-Cre administration into the brain of floxed GluN1 mice [55, 56]. Specificity of the GluN1 antibody was characterized via immunoprecipitation and immunohistochemistry [57–59].…”