Which afferents induce and transmit dorsal root reflex in rats?

The dorsal root reflex (DRR) in single fibers, recorded in the severed L5 dorsal root central stump, initiated spontaneously or by electric stimulation (St) of sciatic nerve, was studied in anesthetized rats. The excitation of group II afferents were the major inputs to induce DRRs which were transmitted mainly in fibers with conduction velocity below 20 m/s, and its central delay was 3-5 ms. The firing frequency of both spontaneous and evoked DRRs were increased two to four times after spinalization (T13). These results suggested that the DRR may play an important role in the modulation of sensory afferent inputs regulated by supraspinal structures.