Functional connectivity between neurons generating resting discharge in renal sympathetic neurons in the rabbit

In anaesthetised rabbits, we analysed the cross-correlations of resting discharges in pairs of simultaneously recorded renal neurons. The study of 428 significant cross-correlations showed three pure types of neuronal co-ordination and two combined effects. Pure shared input was observed in 202 pairs of neurons (47.2%). The width of cross-correlogram peak was 222.9±7.2 ms. The peak height of shared input was 4.8±0.2 spikes s−1 and was significantly related with correlogram width. Pure excitatory connection was found in 24 neuronal pairs (5.6%). Its peak width was 7.9±1.9 ms and it was shifted from time zero by 13.3±3.4 ms. The amplitude of the peak was 19.6±4.6 spikes s−1. In 165 pairs of neurons (38.6%), excitatory connection was combined with shared input component. Pure reciprocal activation was seen in only 5 pairs of neurons (1.1%) while in 32 pairs (7.5%) it was accompanied by shared input co-ordination. The distance between narrow peaks measured in the combined type of co-ordination was 32.5±3.5 ms and the mean peak height was 4.1±0.7 spikes s−1. Shared input in pure form and that accompanying both excitatory connection and reciprocal activation were significantly related to the frequency of discharge of neurons contributing to the cross-correlogram. The incidence and basic properties of the encountered types of neural co-ordination may indicate a pattern of interconnections between cells generating vasomotor tone in renal sympathetic neurons.