Central angiotensin induction of fetal brain c-fos expression and swallowing activity

The present study examined physiological and cellular responses to central application of ANG II in ovine fetuses and determined the fetal central ANG -mediated dipsogenic sites in utero. Chronically prepared near-term ovine f etuses (130 +/- 2 days) received injection of ANG II (1.5 mg/kg icv). Fetus es were monitored for 3.5 h for swallowing activity, after which animals we re killed and fetal brains were perfused for subsequent Fos staining. Intra cerebroventricular ANG II significantly increased fetal swallowing in near- term ovine fetuses (1.1 +/- 0.2 to 4.5 +/- 1.0 swallows/min). The initiatio n of stimulated fetal swallowing activity was similar to the latency of thi rst responses (drinking behavior) elicited by central ANG II in adult anima ls. ANG II evoked increased Fos staining in putative dipsogenic centers, in cluding the subfornical organ, organum vasculosum of the lamina terminalis, and median preoptic nucleus. Intracerebroventricular injection of ANG II a lso caused c-fos expression in the fetal hindbrain. These results indicate that an ANG II-mediated central dipsogenic mechanism is intact before birth , acting at sites consistent with the dipsogenic neural network. Central AN G II mechanisms likely contribute to fetal body fluid and amniotic fluid re gulation.