Stimulation of area postrema decreases blood flow to choroid plexus

The goal of this study was to examine effects of stimulation of the area postrema on blood flow to choroid plexus and brain. In chloralose-anesthetized dogs, the area postrema was stimulated electrically, and arterial pressure and blood gases were maintained at control levels. We measured blood flow to brain and choroid plexus of the fourth and lateral ventricles with microspheres. Stimulation of the area postrema at 10 +/- 2 microA (means +/- SE), which was the threshold for changes in arterial pressure and heart rate, decreased blood flow to choroid plexus of the fourth and lateral ventricles by 41 +/- 11 and 51 +/- 6%, respectively (from 349 +/- 38 and 503 +/- 46 ml.min-1.100 g-1, respectively). Stimulation at high amplitudes (67 +/- 5 microA) produced only slightly greater decreases in blood flow to choroid plexus. In contrast, cerebral blood flow did not change during stimulation of the area postrema. After blockade of autonomic ganglia with intravenous chlorisondamine, stimulation of the area postrema had minimal effects on blood flow to choroid plexus. The results indicate that stimulation of the area postrema decreases blood flow to choroid plexus, probably by an autonomic mechanism. We speculate that the area postrema may play a role in regulation of volume in the central nervous system by modulating production of cerebrospinal fluid.