The dorsal root reflex (DRR) in single fibers, recorded in the severed L5 dorsal root central stump, initiated by sciatic nerve (SN) stimulation (St), was studied in anesthetized rats. Both ipsi- and contralateral Sts elicited DRR, with central delays of 4.6±0.3 (n=10) and 27.3±2.5 (n=5) ms, respectively. Ipsilaterally induced DRRs showed repetitive firing (mean=3±0.5 spikes, n=5), while contralaterally induced ones were abolished after spinalization (T13). When the time interval between two ipsilateral suprathreshold Sts was less than 12±2.4 ms (n=12), the second DRR was abolished. On the other hand, when it between two ipsilateral subthreshold Sts was less than 4.8±0.3 ms (n=7), DRR was activated. Contralaterally induced DRR also showed temporal inhibition and facilitation with time intervals similar to that in ipsilateral cases. Furthermore, when the latency between a contralaterally and a ipsilaterally induced DRR was less than 10.8±1.8 ms (n=5), the later DRR was blocked by the former, and vice versa. Facilitation can be also shown by a contralateral and a ipsilateral subthreshold St. These results suggested that contralaterally induced DRRs may share part of final common pathway with ipsilaterally induced ones. Copyright (C) 1999 Elsevier Science Ireland Ltd.
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