Sl. Hochstenbach et J. Ciriello, PLASMA HYPERNATREMIA INDUCES C-FOS ACTIVITY IN MEDULLARY CATECHOLAMINERGIC NEURONS, Brain research, 674(1), 1995, pp. 46-54
Experiments were done in conscious rats to investigate the effect of i
ntravenous infusion of hypertonic saline on the induction of the phosp
hoprotein Fos in brainstem catecholaminergic neurons. Fos induction, d
etected immunohistochemically, was used as a marker for neuronal activ
ation. Infusions of 165 mM or 1.4 M NaCl solutions into the jugular ve
in resulted in Fos-like immunoreactivity in approximately the caudal t
wo thirds of nucleus of the solitary tract (NTS), the caudal and rostr
al ventrolateral medulla (VLM), and in the lateral aspects of the para
brachial nucleus (PEN). Within caudal NTS a small number (7.9+/-1.8%)
of Fos labelled neurons were found also to contain tyrosine hydroxylas
e (TH) or dopamine beta-hydroxylase (DBH) immunoreactivity. In rostral
NTS no Fos labelled cells were found to contain phenylethanolamine N-
methyltransferase (PNMT) immunoreactivity, although a few (8.5+/-2.3%)
were immunoreactive to TH. Similarly, in VLM, most of the Fos labelle
d cells in caudal VLM (65.9+/-2.7%) contained either TH or DBH immunor
eactivity, whereas in the rostral VLM, 32.2+/-4.6% of the Fos labelled
cells were also immunoreactive to TH or DBH. However, no Fos cells we
re found in either the caudal or rostral VLM that were immunoreactive
to PNMT. Little or no Fos-like immunoreactive neurons were detected in
the brainstem after intravenous infusions of physiological (143 mM) o
r hypotonic (106 mM) NaCl solutions. These data suggest that noradrene
rgic neurons of the caudal NTS and VLM are components of central circu
its that are involved in osmoregulation and cardiovascular function.