Distinct neurochemical populations in the rat central nucleus of the amygdala and bed nucleus of the stria terminalis: Evidence for their selective activation by interleukin-1?

Abstract

The lateral division of the central nucleus of the amygdala (CEAl) and the oval nucleus of the bed nucleus of the stria terminalis (BSTov) have been linked closely anatomically and functionally. To determine whether these regions may be subdivided further on a neurochemical basis, dual in situ hybridization was used to determine the colocalization of corticotropinreleasing hormone (CRH), enkephalin (ENK), or neurotensin (NT) with glutamic acid decarboxylase isoforms 65 and 67 [used concurrently as a marker for ␥-aminobutyric acid GABA] in these nuclei. It was found that, for both regions, each peptide invariably was localized in a GABAergic cell. Although there was a similar overlap in the distribution of NT with ENK in the BSTov and CEAl, it was observed that CRH and ENK rarely were colocalized in either nucleus. To determine whether these distinct neuronal populations could be activated differentially, male rats were given a systemic injection of interleukin-1␤ (IL-1␤; 5 µg/kg, i.p.), a stimulus that results in a robust increase in c-fos mRNA expression in the BSTov and CEAl. The neurochemical identity of these activated neurons showed striking similarities between the BSTov and the CEAl; All IL-1␤-responsive cells were GABAergic, the majority of c-fos-positive cells expressed ENK mRNA (BSTov, 81%; CEAl, 94%), and some expressed NT mRNA (BSTov, 23%; CEAl, 22%), whereas very few expressed CRH mRNA (BSTov, 4%; CEAl, 1%). These data provide evidence for the existence of discrete neural circuits within the BSTov and CEAl, and the similarities in the patterns of neurochemical colocalization in these nuclei are consistent with the concept of an extended amygdala. Furthermore, these data indicate that intraperitoneal IL-1␤ recruits neurochemically distinct pathways within the BSTov and CEAl, and it is suggested that this differential activation may mediate specific aspects of immune, limbic, and/or autonomic processes.

The central and basolateral nuclei of the amygdala exhibit opposite diurnal rhythms of expression of the clock protein Period2

“…An additional observation that we made is that cells within the CEA and BNST-OV that express PER2 are immunoreactive to ENK but not to CRF. This observation is interesting in light of findings that ENK cells of the CEA and BNST-OV are particularly sensitive to the effect of stressors and drugs as assessed by c-fos gene expression (63)(64)(65).…”

A Circadian Rhythm in the Expression of PERIOD2 Protein Reveals a Novel SCN-Controlled Oscillator in the Oval Nucleus of the Bed Nucleus of the Stria Terminalis

“…Interestingly, restricted feeding schedules, which entrain circadian activity rhythms via SCN-independent clocks (Stephan et al, 1979), have also been shown to disrupt coupling between the SCN and other brain and peripheral oscillators (Damiola et al, 2000;Stokkan et al, 2001). Neurons in the BNST-OV are sensitive to food restriction (Carr et al, 1998;Carr and Kutchukhidze, 2000) and are activated by treatment with anorectic agents (Bonaz et al, 1993;Li and Rowland, 1995;Day et al, 1999), suggesting the intriguing possibility that oscillations of cells of the BNST-OV might be regulated directly by food-related stimuli.…”

β1 Adrenergic Receptors in the Bed Nucleus of Stria Terminalis Mediate Differential Responses to Opiate Withdrawal

“…The BST contains multiple peptide populations coexpressed in GABAergic neurons, with the clearest separation between corticotropin-releasing factor (CRF)-expressing and enkephalin-expressing populations (Day et al, 1999). Microinjection of b antagonists into BST blocks anxiety-like behavior in the elevated plus-maze, and reduces stress-induced reinstatement of drug-seeking behavior (Cecchi et al, 2002;Leri et al, 2002).…”