FOS INDUCTION IN CENTRAL STRUCTURES AFTER AFFERENT RENAL NERVE-STIMULATION

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.