Excitatory and inhibitory interactions among renal and cardiovascular afferent nerves in dorsomedial medulla.

Central interactions between renal afferent nerves (RN) and carotid sinus (CSN) and aortic (AN) nerves were investigated by recording extracellular action potentials from single units in and around the nucleus tractus solitarius (NTS) in alpha-chloralose-anesthetized cats. Forty-nine units were activated by electrical stimulation of the renal nerve; twenty-seven of these also were excited by CSN, AN, or both. Summation of inputs was demonstrated during simultaneous subthreshold or suprathreshold stimulation of RN and CSN or AN. In 10 units excited by simultaneous stimulation of RN and AN or CSN, a conditioning stimulus (333 Hz for 10 ms) applied to RN caused prolonged (up to 150 ms) inhibition of responses to stimulation of AN or CSN; reciprocal inhibitory interactions were also shown. These studies show that renal afferent input interacts with cardiovascular afferent input at neurons in the NTS region of dorsal medulla and suggest that the outcome of these interactions at the single cell level may be critically dependent on the temporal relationships among afferent impulses converging on common central synapses.