Projections of laminae IV-VI neurones located in the S2 segment of the spinal cord to the C6 segment and the cerebellum in the cat.

Abstract

Ascending projections of neurones of the second sacral segment (S2) of the spinal cord to the sixth cervical segment (C6) and to the cerebellum were electrophysiologically investigated in eight adult cats under alpha-chloralose anaesthesia. Antidromic potentials recorded from 44 neurones following stimulation of their axons in the grey matter of the C6 segment as well as in the contralateral restiform body (coRB) showed evidence of both supraspinal and propriospinal projections. About one third of neurones (15) ascended to the cerebellum through the coRB and gave off collaterals to the C6 segment, while the rest (29) terminated exclusively at the level of the C6 segment. The cell bodies were found mainly in central parts of Rexed' s laminae IV, V and VI while axons ran in lateral funiculi. Axonal conduction velocities measured between S2 and C6 segments were in the range of 42-78 m/s. A decrease of conduction velocity above the Th13 and C6 segments was found in most axons suggesting that they give some collaterals at spinal as well as supraspinal levels.