Spinal projections of cat primary afferent fibers innervating caudal facetjoints

The spinal projections of afferent fibers innervating the facet joints betw een caudal vertebrae were examined by the use of anterograde transport of w heat germ agglutinin-horseradish peroxidase (WGA-HRP). Experiments were per formed on 5 adult cats in which spinal dorsal roots below the 2nd sacral se gment (S2) on the right side were cut. Injections of WGA-HRP into the cauda l Facet joints gave rise to extensive cranio-caudal distribution of WGA-HRP positive products along the spinal cord, indicating that many afferent fib ers innervating unilateral facet joints terminate bilaterally in laminae I- II, V-VI and X of the thoracic, lumbar, sacral and caudal spinal cord. Thes e afferent fibers may convey a series of sensory information from the cauda l facet joints to the spinal cord.