Electrophysiological investigation of spino - olivary projections originating from sacral segments of the cat spinal cord

Ascending projections of sacral spinal cord neurones (S1-S2) to the dorsal accessory olivary nucleus (DAO) were electrophysiologically investigated in 3 adult cats under deep Beta-chloralose anaesthesia. Antidromic action potentials were recorded extracellularly from 19 cells following stimulation of their axons in both the contralateral dorsal accessory olivary nucleus (coDAO) and the contralateral lateral funiculus at the level of lower thoracic segments (Th13). Two groups of neurones were identified in the gray matter of S1-S2 segments: one distributed in the medial part of Rexed’s laminae VI and VII (n = 5), the other located in the ventromedial part of lamina VIII (n = 14). Axonal conduction velocities of neurones investigated were comprised in the range 32-55 m/s. A significant decrease of conduction velocity was observed in each case when distal and proximal parts of the axon were compared. Our research confirmed anatomical data concerning spino-olivary neurones originating from sacral segments. However, we suggest that axons of this pathway give off collaterals to other spinal or supraspinal centres.