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Abstract
The dorsal vagal complex (DVC) encompasses the nucleus tractus solitarii (NTS), the
dorsal motor nucleus of the vagus nerve (DMX) and the area postrema (AP), that altogether
provide the major integrative center for the mammalian autonomic nervous system. The
adult rat DVC has been reported to contain afferent-dependent concentration of the
plasticity-promoting polysialylated form of neural cell adhesion molecule [J Neurosci
21 (2001) 4721; Eur J Neurosci 14 (2001) 1194]. This prompted us to assess the occurrence
of neurogenesis in the DVC of adult rats. Cumulative in vivo labeling of cell proliferation
with i.p. bromodeoxyuridine (BrdU) injections was combined with phenotypic markers
and confocal microscopy on serial brainstem sections throughout the DVC extent. In
basal condition, sparse BrdU+ nuclei were selectively detected in the DVC according
to a discrete and reproducible pattern. Some of them were found to colocalize with
the neuronal markers doublecortin, HuC/D, or neuronal-specific antigen (NeuN), demonstrating
that neurogenesis does occur within the DVC of adult rat. In the NTS, 10% of the BrdU+
nuclei were also NeuN+. A comparable proportion of astrogliogenesis was found in the
DVC. Nestin immunohistochemistry yielded a highly specific labeling pattern at the
border between AP and NTS. These data may relate to the neural stem cells that have
been reported in the floor of the IVth ventricle [J Neurosci 16 (1996) 7599]. In order
to assess a possible modulation of neurogenesis by afferent input in vivo, unilateral
vagotomy was performed prior to cumulative BrdU treatment. Such DVC deafferentation
triggered a large increase of BrdU incorporation in the ipsilateral DVC, which was
associated with microglial proliferation in the DMX and with increased genesis of
neurons and astrocytes in the NTS. These findings establish DVC as a novel model of
adult neurogenesis that is reactive to deafferentation.