Glial fibrillary acidic protein (GFAP)-positive radial-like cells are present in the vicinity of proliferative progenitors in the nucleus tractus solitarius of adult rat.

The dorsal vagal complex (DVC), an integrative center of autonomic functions located dorsally in the caudal brainstem, comprises the nucleus tractus solitarius (NTS), the area postrema (AP), and the dorsal motor nucleus of the vagus nerve (DMNX). Recently, this area of the brainstem was shown to retain, during adulthood, the expression of developmental markers, which is consistent with several forms of morphological and functional plasticity. These data led us to attempt to determine the structural organization and phenotypical characteristics of the astroglial compartment in the adult DVC. We report a strikingly high density of glial fibrillary acidic protein (GFAP) immunoreactive cells in the NTS and the DMNX compared to other brainstem structures. Furthermore, we observed a subpopulation of atypical GFAP+ cells in the NTS. These cells expressed vimentin and nestin and displayed unbranched processes that radiate rostrocaudally from cuboid cell bodies located in the 4th ventricle wall. Interestingly, these radiating cells were found in close association with neural progenitors whose proliferation was stimulated by intracerebroventricular injection of epidermal growth factor/basic fibroblast growth factor or lesion of the vagus nerve. Newly born neurons in the NTS identified by doublecortin (DCX) immunolabeling were also preferentially found in the vicinity of the radiating cells. Altogether, these results indicate that the adult NTS retains, during adulthood, astroglial cells that display morphological and phenotypical features seen during development. The overlap in the distribution of proliferative neural progenitors, newborn neurons, and radiating GFAP-positive cells suggest a possible role of the glial compartment of the NTS in functional plasticity in this structure.