Experiments were done in the conscious and unrestrained rat to identif
y central structures activated by electrical stimulation of afferent r
enal nerves (ARN) using the immunohistochemical detection of Fos-like
proteins. Fos-labelled neurons were found in a number of forebrain and
brainstem structures bilaterally, but with a contralateral predominan
ce. Additionally, Fos-labelled neurons were found in the lower thoraco
lumbar spinal cord predominantly ipsilateral to the side of ARN stimul
ation. Within the forebrain, neurons containing Fos-like immunoreactiv
ity after ARN stimulation were primarily found along the outer edge of
the rostral organum vasculosum of the laminae terminalis, in the medi
al regions of the subfornical organ, in the median preoptic nucleus, i
n the ventral subdivision of the bed nucleus of the stria terminalis,
along the lateral part of the central nucleus of the amygdala, through
out the deeper layers of the dysgranular insular cortex, in the parvoc
ellular component of the paraventricular nucleus of the hypothalamus (
PVH), and in the paraventricular nucleus of the thalamus. Additionally
, a smaller number of Fos-labelled neurons was observed in the supraop
tic nucleus, in the magnocellular component of the PVH and along the l
ateral border of the arcuate nucleus. Within the brainstem, Fos-labell
ed neurons were found predominantly in the commissural and medial subn
uclei of the nucleus of the solitary tract and in the external subnucl
eus of the lateral parabrachial nucleus. A smaller number were observe
d near the caudal pole of the locus coeruleus, and scattered throughou
t the ventrolateral medullary and pontine reticular formation in the r
egions known to contain the A1, C1 and A5 catecholamine cell groups. T
he final area observed to contain Fos-labelled neurons in the central
nervous system was the thoracolumbar spinal cord (T9-L1) which contain
ed cells in laminae I-V of the dorsal horn ipsilateral to side of stim
ulation and in the intermediolateral cell column at the same levels bi
laterally, but with an ipsilateral predominance. Few, if any Fos-label
led neurons were observed in the same structures of control animals in
which the ARN were stimulated, but the renal nerves proximal to the s
ite of stimulation were transected, or in the sham operated animals. T
hese data indicate that ARN information originating in renal receptors
is conveyed to a number of central areas known to be involved in the
regulation of body fluid balance and arterial pressure, and suggest th
at this afferent information is an important component of central mech
anisms regulating these homeostatic functions. (C) 1997 Elsevier Scien
ce B.V.