Electrophysiological evidence of baroreceptor input to area postrema

Subpopulations of rat area postrema (AP) and nucleus tractus solitarius (NTS) neurons exist that are responsive to changes in blood pressure. The hypothesis that these effects may be mediated by afferent baroreceptor input was examined. Orthodromic responses of AP and NTS neurons to aortic depressor nerve (ADN) stimulation were observed. Sixty-three percent of AP neurons were affected by ADN stimulation, with most exhibiting short-duration excitatory responses (latency, 27 +/- 1 ms; duration, 11 +/- 1 ms). Fifty-five percent of NTS neurons were influenced by ADN stimulation, although effects in this region were more heterogeneous (24% of neurons excited, 31% inhibited). Thus, in the rat, apparently both AP and NTS neurons receive afferent barosensory information.