Immunohistochemical localization of GAD67‐expressing neurons and processes in the rat brainstem: Subregional distribution in the nucleus tractus solitarius

Abstract

The role of gamma-aminobutyric acid (GABA) in homeostatic control in the brainstem, in particular, in the nucleus tractus solitarius (NTS), is well established. However, to date, there is no detailed description of the distribution of GABAergic neurons within the NTS. The goal of the current study was to reexamine the efficacy of immunohistochemical localization of glutamic acid decarboxylase (GAD) protein, specifically the 67-kDa isoform (GAD67), as a marker for GABAergic neurons in the medulla and to provide a detailed map of GAD67-immunoreactive (-ir) cells within rat NTS by using a recently developed mouse monoclonal antibody. We describe a distribution of GAD67-ir cells in the medulla similar to that reported previously from in situ hybridization study. GAD67-ir cells were localized in regions known to contain high GABA content, including the ventrolateral medulla, raphe nuclei, and area postrema, but were absent from all motor nuclei, although dense terminal labeling was discerned in these regions. In the NTS, GAD67-ir was localized in all subregions. Semiquantitative analysis of the GAD67-ir distribution in the NTS revealed greater numbers of GAD67-ir cells medial to the solitary tract. Finally, dense GAD67 terminal labeling was found in the medial, central, intermediate, commissural, and subpostremal subregions, whereas sparse labeling was observed in the ventral subregion. Our findings support the use of immunohistochemistry for GAD67 as a marker for the localization of GABAergic cells and terminal processes in the rat brainstem. Furthermore, the reported heterogeneous distribution of GAD67-ir in the NTS suggests differential inhibitory modulation of sensory processing.

GABA signaling in the nucleus tractus solitarius sets the level of activity in dorsal motor nucleus of the vagus cholinergic neurons in the vagovagal circuit

“…The robust effect on gastric tone observed with blockade of GABA A receptors in the area of the mNTS proves that GABA is present in this area and is exerting a powerful activation on GABA A receptors. This is corroborated by in situ hybridization and immunocytochemical studies (13) that report that the mNTS contains the densest labeling of GABAergic interneurons in the entire NTS.…”

“…3). The first view persists despite both anatomical and functional in vitro evidence of local inhibitory processing within the NTS (13,15,17,21). The second view lacks functional evidence for the NANC pathway as it relates to gastric motility (8,18).…”

Expression of PTPRO in the interneurons of adult mouse olfactory bulb

“…The staining pattern of CB in adult mouse OB in this study was identical to that in previous reports, in which the rabbit pAb to recombinant rat CB (Swant, Belinzona, Switzerland; CB-38) or the mouse mAb to bovine kidney CB (Sigma, St; Louis, MO; C-9848) was used (Parrish-Aungst et al, 2007;Batista-Brito et al, 2008). GAD67-The mouse mAb to GAD67 recognized a single band of 67 kDa on immunoblot of rat cerebellar cortex (Fong et al, 2005). Immunohistochemistry of rat medulla showed a pattern similar to that reported previously from an in situ hybridization study (Fong et al, 2005).…”

Neural Pathways Underlying Lactate-Induced Panic

“…This circuit represents an adaptive means of inhibiting the baroreflex during 'fight or flight' responses and exercise (Potts et al, 2003). The nTS contains numerous GABAergic neurons (Fong et al, 2005) which could be dampening parasympathetic activity by inhibiting acetylcholinergic vagal preganglionic neurons. This notion is supported by recent evidence that stimulation of nTS neurons in vitro inhibits DMV neurons (Davis et al, 2003;Sevoz-Couche et al, 2003).…”