HYPOTHALAMIC NEURONS WITH ACTIVITY PATTERNS RELATED TO SYMPATHETIC-NERVE DISCHARGE

Spike-triggered averaging was used to identify hypothalamic neurons with activity patterns related to inferior cardiac sympathetic nerve discharge (SND). Three neuronal types were identified in baroreceptor-innervated cats. The discharges of SR units were temporally related to SND and the R wave of the ECG. The discharges of SER units were in addition related to EEG activity. SE unit discharges were related to SND and EEG activity but not to the R wave. Two neuronal types were identified in baroreceptor-denervated cats. The discharges of S units were temporally related to SND but not to EEG activity. The 2nd neuronal type exhibited activity patterns similar to those for SE neurons in the baroreceptor-innervated cat. With the exception of SER neurons, all unit types could be subdivided into 2 groups depending on whether their discharges were followed by an increase or a decrease in SND. The discharges of SER units were followed by a decrease in SND. These data are discussed with regard to the role played by the hypothalamus in generating the basal discharges of sympathetic nerves.