Abstract

Mapping of amygdalar sub-nuclei: A comparative study

Sharma V, Medina A, Krolewski DM, Burke S, Fitzpatrick J, Jones EG, Bunney WE, Myers RM, Schatzberg AF, Barchas JD, Akil H, Watson SJ
Society for Neuroscience. 2011.

The amygdala is a collection of sub-cortical nuclei in the telencephalon that plays a major role in regulating physiological or autonomic behaviors as well as higher cognitive functions like attention, emotion, memory and decision-making. This elaborate repertoire of functions relies upon its various sub-nuclei and their extensive connections. However, there is no consistent anatomical description of these sub-nuclei across various species especially in humans. Therefore, we aim to prepare a comprehensive anatomical map based on the differential expression of specific transcripts in various sub-nuclei of human amygdala and to compare it with the rat using in situ hybridization (ISH) combined with histological techniques. Human brain samples were obtained from the Brain Repository at the University of California, Irvine and Davis. The blocks containing the amygdala region were cryo-sectioned at 10µm thickness. Sections at intervals of 500µm and 50µm for human and rat brains respectively were used for ISH. For identifying the sub-nuclei, adjacent sections were stained for acetylcholinestrase. We used 35S cRNA probes for CR, Enk, CCK, NPY, Substance P and AVP for delineating the sub-nuclei of amygdala. Digitized images were generated using Adobe Photoshop CS2 with the probe signals color coded and overlaid to visualize differential gene expression patterns in different sub-nuclei across various species. NPY is distributed across the whole amygdala. Substance P is predominantly expressed in the lining of the paralaminar zone and medial sub-nuclei. CR and CCK are expressed prominently in the ventromedial region of human amygdala. Enk is concentrated in the centro-medial subnuclear region of amygdala. AVP is exclusively expressed in the periamygdaloid cortex. These differential expression patterns of various genes will help to make a comprehensive anatomical map defining amygdala sub nuclei across various species and to identify the role played by each sub-nucleus in the extensive functions of the amygdala.