Contralaterally induced dorsal root reflex shares common final pathway with ipsilaterally elicited ones in Wistar rats

The dorsal root reflex (DRR) in single fibers, recorded in the severed L5 d orsal root central stump, initiated by sciatic nerve (SN) stimulation (St), was studied in anesthetized rats. Both ipsi- and contralateral Sts elicite d 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 (mea n = 3 +/- 0.5 spikes, n = 5), while contralaterally induced ones were aboli shed after spinalization (T13). When the time interval between two ipsilate ral 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 subthres hold Sts was less than 4.8 +/- 0.3 ms (n = 7), DRR was activated. Contralat erally induced DRR also showed temporal inhibition and facilitation with ti me intervals similar to that in ipsilateral cases. Furthermore, when the la tency between a contralaterally and a ipsilaterally induced DRR was less th an 10.8 +/- 1.8 ms (n = 5), the later DRR was blocked by the former, and vi ce versa. Facilitation can be also shown by a contralateral and a ipsilater al subthreshold St. These results suggested that contralaterally induced DR Rs may share part of final common pathway with ipsilaterally induced ones. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.