Neuronal architecture in the rat central nucleus of the amygdala: A cytological, hodological, and immunocytochemical study

Abstract

The organization of neurons in the rat central nucleus of the amygdala (CNA) has been examined by using Nissl stain and immunocytochemical and retrograde tracing techniques. Four main subdivisions were identified on the basis of quantitative analyses of Nissl-stained material: medial (CM), lateral (CL), lateral capsular (CLC), and ventral (CV). An intermediate subdivision (CI), previously described by McDonald ('82), was apparent only in animals that had HRP-WGA injected into the bed nucleus of the stria terminalis. Large populations of neurotensin-, corticotropin-releasing factor (CRF)-, and enkephalin-immunoreactive neurons were present within the lateral divisions (mainly CL), although they were also seen within CM. Somatostatin-immunoreactive neurons were distributed mainly within CL and CM. Within CL, neurotensin- and enkephalin-immunoreactive neurons were more numerous laterally whereas CRF- and somatostatin-immunoreactive neurons were more numerous medially. Substance P-immunoreactive neurons were almost exclusively confined to CM. Only a few cholecystokinin- and vasoactive-polypeptide-immunoreactive neurons were seen in the CNA, and they were observed within CL, CV, and CM. The majority of neurons projecting to the dorsal medulla, hypothalamus, and ventral tegmental area were located within CM, although a significant number of cells were also seen within CL. Efferent projections to the bed nucleus of the stria terminalis were found to arise from neurons located within all subdivisions of the CNA. Thus, the distributional patterns of peptidergic and efferent neurons were not confined to individual cytoarchitectonically- defined subdivisions of the CNA. Rather, the results suggest overlapping medial to the lateral trends. Comparisons with the results of previous studies indicate that peptidergic and afferent terminal distribution patterns are more restricted to individual cytoarchitectonically defined subregions of the CNA. These observations suggest that the detailed cytoarchitecture of the CNA more likely reflects the functional integration of afferents rather than the organization of the CNA output neurons.

Postnatal development of the amygdala: A stereological study in rats

“…The nomenclature and the basic description of the morphological characteristics of the rat amygdala nuclei have been described in detail previously (Cassell et al, 1986;Jolkkonen and Pitk€ anen, 1998;Krettek and Price, 1978;McDonald, 1982;Pitk€ anen, 2000;Pitk€ anen et al, 1995;Price et al, 1987;Savander et al, 1995Savander et al, , 1996. We used these descriptions to determine the boundaries of the five main nuclei (i.e., lateral, basal, accessory basal, central, and medial) of the rat amygdala ( Fig.…”

“…The absence of changes in volume of the medial nucleus from 1 to 2 weeks of age could be explained by the fact that the Mpd represents only $50% of the medial nucleus volume (Cooke et al, 2000), and volume changes induced by the reorganization of this unique type of interconnections with the BNST might be too marginal to be observed. However, it is well established that the BNST is a major target of central amygdala projection neurons (Cassell et al, 1986;Zahm et al, 1999), and, although not yet investigated, such connectional reorganization between the central amygdala and the BNST could potentially explain the increase in volume of the central nucleus from 1 to 2 weeks of age. In sum, the subtle volumetric changes of the rat central and medial nuclei during the first postnatal weeks might reflect the minimal structural (and potentially functional) refinement of the interconnections between these nuclei and the rest of the brain after 1 week of age.…”

What is the bed nucleus of the stria terminalis?

“…Information likely flows into the BST from exteroceptive (main and accessory olfactory, touch and nociception, gustatory) or interoceptive (energy and fluid levels, tissue damage, sexual hormone levels) sources through all central nervous system levels (from cortical to brain stem and spinal cord). The BST then has widespread descending projections to motor regions of the hindbrain that may trigger or contribute to the elaboration of coordinated physiological and behavioural responses necessary for a well-balanced homeostasis.The BST can be roughly divided into anterior and posterior subdivisions, each containing several nuclei, which can be identified based on their projection pattern and neurochemical identity (Cassell et al, 1986;Day et al …”

“…The BST can be roughly divided into anterior and posterior subdivisions, each containing several nuclei, which can be identified based on their projection pattern and neurochemical identity (Cassell et al, 1986;Day et al…”

“…The BST can be roughly divided into anterior and posterior subdivisions, each containing several nuclei, which can be identified based on their projection pattern and neurochemical identity (Cassell et al, 1986;Day et al, 1999;Larriva-Sahd, 2004, 2006McDonald,1983;Moga et al,1989;Veinante and Freund-Mercier, 1997 posterior group (BSTpost) may contribute more to reproduction and defense. However, the anterior and posterior BST are highly interconnected, ruling out unrelated or distinct functions for the two general areas.…”