Permanent loss of fore-paw grasping requires complete deprivation of afferent input from a minimum of four dorsal roots of the rat brachial plexus.

ABSTRACT

Dorsal roots from the 6th cervical to the 1st thoracic segment were sectioned flush with the surface of the spinal cord on one side. For 3 weeks before and 8 weeks after surgery the rats were filmed once a week during two successive climbs up a 1 m grid. Before surgery the fore-paws of normal rats grasped the grid bar for a mean of 7.0+/-0.1 times per climb. After complete section of C6 to T1 dorsal roots on one side there was a major deficit in the ipsilateral fore-paw in locating the grid bars, and grasping was almost totally abolished (mean of 0.1+/-0.06 grasps per climb). The failure of the rats to locate or to grasp the bars persisted unchanged for the entire test period. Rats with section of C6 to C8, but sparing T1, showed a similar but milder pattern of deficit. Section of any two adjacent cervical roots caused only minor deficits. Section of any single root alone caused no detectable deficit in climbing. The consistent loss of grasping after section of the 4 dorsal roots from C6 to T1 provides a promising model for assessing putative regenerative therapies.