Characteristics of dorsal root potentials recorded from the isolated spinal cord of the neonate rat.

Dorsal root potentials (DRP) and dorsal root reflexes (DRR) have been recorded from the isolated cord of the neonate rat. A single stimulus to the adjacent rostral or adjacent caudal dorsal root or dorsal columns evoked a DRP, the peak amplitude of which was reached in 110--115 msec and which decayed exponentially over most of its time course (time constant 800--850 msec). The same stimuli evoked field potentials in the dorsal horn comprising fast negative, slow negative and slow positive potentials. DRP had a lower threshold than DRR and reached a maximal amplitude at stimulus voltages sub-maximal for DRR. Increasing the intensity of stimulation shortened the latency of DRP and prolonged its time course. DRR and DRP were depressed by a prior conditioning stimulus (CS) and by the addition of Mg++ ions to the bathing solution. A CS was more effective in producing depression of responses evoked more rostrally than more caudally.