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 effects of paraventricular nucleus (PVN) stimulation on these cells from anesthetized Sprague-Dawley rats. Of 91 AP cells tested, 30.8% responded 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-PVN), only 4 of the 72 AP cells tested (5.6%) were influenced by stimulation. These excitatory effects of PVN stimulation on AP neurons were unaffected by V1-receptor blockade. Of 93 nucleus of the solitary tract (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) excitation 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 influenced only 19% of NTS neurons tested, all of which were excited. These data demonstrate that activation of PVN neurons elicits excitatory effects on the majority of AP neurons influenced. They further emphasize the potential significance of descending hypothalamic inputs in controlling neuronal activity in this circumventricular organ.