PARAVENTRICULAR NUCLEUS EFFERENTS INFLUENCE AREA POSTREMA NEURONS

Extracellular single-unit recordings were obtained from area postrema neurons (AP), and peristimulus histograms were used to determine the e ffects of paraventricular nucleus (PVN) stimulation on these cells fro m anesthetized Sprague-Dawley rats. Of 91 AP cells tested, 30.8% respo nded to PVN stimulation with a short-latency (28.2 +/- 3.3 ms, mean +/ - SE), short-duration (49.3 +/- 8.0 ms) excitation, whereas 8.6% were inhibited. In animals that had stimulation sites outside of PVN (non-P VN), only 4 of the 72 AP cells tested (5.6%) were influenced by stimul ation. These excitatory effects of PVN stimulation on AP neurons were unaffected by V-1-receptor blockade. Of 93 nucleus of the solitary tra ct (NTS) cells tested, 38.9% responded to PVN stimulation with a short -latency (18.5 +/- 2.4 ms), short duration (48.8 +/- 9.6 ms) excitatio n and 22.2% with short-latency (20.75 +/- 4.1 ms), long-duration (204. 4 +/- 44.9 ms) inhibitions. In contrast, non-PVN stimulation sites inf luenced only 19% of NTS neurons tested, all of which were excited. The se data demonstrate that activation of PVN neurons elicits excitatory effects on the majority of AP neurons influenced. They further emphasi ze the potential significance of descending hypothalamic inputs in con trolling neuronal activity in this circumventricular organ.