Dorsal root potentials (DRPs) and dorsal cord potentials (DCPs) were recorded from the lumbar spinal cord in anaesthetised rats. With the spinal cord intact, low-voltage low-frequency spontaneous DRPs were recorded in synchrony on all lumbar dorsal roots. When the cord was cut at T12, spontaneous large-voltage approximately 10 Hz DRPs appeared immediately in synchrony on all dorsal roots. Section of the dorsolateral funiculus (DLF) was necessary to release these 10 Hz waves. They persisted unchanged for at least 2 h and were not affected by section of all lumbar, sacral and coccygeal dorsal roots. Selective transverse lesions were made to locate the fibres responsible for the synchrony of the oscillations of DRPs recorded on L1 and L6 dorsal roots. Synchrony was maintained with lesions of the entire cord medial to the Lissauer tract but disappeared when the lesion was extended to include the Lissauer tract. We conclude that the isolated cord contains a synchronous oscillatory mechanism inhibited by impulses descending in the DLF and synchronised by way of intrinsic axons in the Lissauer tract.
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