Clonidine diminishes c- jun gene expression in the cardiovascular sensitive areas of the rat brainstem

Abstract

The present study investigated the effect of clonidine on the basal and inducible c- jun and c- fos mRNA expression in the nucleus tractus solitarius (middle, mNTS, and rostral, rNTS) and the rostral ventrolateral medulla (caudal, cRVLM, and rostral, rRVLM). Conscious rats received saline, clonidine (30 μg/kg, i.v.), saline plus sodium nitroprusside (NP), or clonidine plus NP. Under basal conditions (saline-infused rats), c- jun mRNA was expressed in the mNTS and rRVLM but not in the rNTS or cRVLM whereas c- fos mRNA was not detectable. Clonidine attenuated the increases in c- fos in the mNTS and cRVLM and c- jun gene expression in the mNTS and rRVLM caused by NP-evoked hypotension and also reduced the basal expression of c- jun mRNA in the mNTS and rRVLM. These findings establish a causal link between clonidine inhibition of c- fos expression in brainstem and its hypotensive action, and provide the first evidence that clonidine attenuates the expression of the closely linked c- jun gene in neurons implicated in centrally mediated hypotension.