COMPARISON OF C-FOS EXPRESSION IN THE LAMINA TERMINALIS OF CONSCIOUS RATS AFTER INTRAVENOUS OR INTRACEREBROVENTRICULAR ANGIOTENSIN

Fos immunoreactivity in the rat brain after intracerebroventricular (I CV) angiotensin II (ANG II) was compared with that induced by intraven ous ANG II. ANG II was infused into the lateral ventricle (at 1 ng/min ) or femoral vein (at 5 mu g/h) of conscious rats. After 90 min, rats were killed and Fos was detected by immunohistochemistry. Both infusio ns caused res immunoreactivity to be present in the lamina terminalis, hypothalamic supraoptic, and paraventricular nuclei, bed nucleus of t he stria terminalis, and central amygdaloid nucleus. However, distribu tions of Fos immunoreactivity within the lamina terminalis differed wi th the different routes of infusion, Intravenous ANG II caused intense Fos immunoreactivity mainly in the subfornical organ (SFO) and organu m vasculosum of the lamina terminalis (OVLT). By contrast, ICV ANG II caused intense Fos immunoreactivity predominantly in the median preopt ic nucleus and juxtaventricular neurons of the SFO and OVLT. These res ults suggest that IV ANG II induces behavioural and endocrine response s by direct actions on the SFO and OVLT, whereas ICV ANG II directly s timulates neurons in the median preoptic nucleus as well neurons in th e SFO and OVLT.