Cardiovascular afferent inputs to ventral tegmental area

Extracellular single-unit recording experiments were done in alpha-chloralose-anesthetized, paralyzed, and artificially ventilated rats to investigate the effect of selective activation of arterial baroreceptors and stimulation of cardiovascular depressor sites in the nucleus of the solitary tract (NTS) on the discharge rate of neurons in the ventral tegmental area (VTA). Electrical stimulation of the aortic depressor nerve (ADN), which is known to carry aortic baroreceptor afferent fibers only, excited 12 of 21 (mean onset latency 42.4 +/- 8.8 ms) and inhibited 2 of 21 (mean onset latency 42.5 +/- 6.5 ms) single units in the VTA. The discharge rate of VTA units was also altered during the reflex activation of arterial baroreceptors by the acute rise in arterial pressure (AP) to systemic injections of phenylephrine (10 micrograms/kg i.v.): 12 of 44 units were excited and 15 of 44 were inhibited. Units that responded to either ADN stimulation or the reflex activation of the baroreflex also responded to stimulation of depressor sites in the NTS. An additional 12 units that were found in barodenervated controls to be responsive to NTS stimulation were nonresponsive to selective activation of arterial baroreceptors. These data indicate that cardiovascular afferent inputs modulate the activity of neurons in the VTA and suggest that changes in systemic AP may exert an effect on the activity of neurons involved in mesolimbic and mesocortical function.