Glucose utilization is unchanged in red nucleus after axotomy

Separate series of adult rats were subjected to unilateral high cervical and low thoracic section of the rubrospinal tract and sacrificed 1-30 (cervical series) and 3-100 days (thoracic series) later. Local cerebral glucose utilization ([14C]2-DG method of Sokoloff et al.) was determined in the red nucleus and in the inferior colliculus, nucleus interpositus and sensorimotor cortex of both sides in operates and controls. Although severe atrophy of rubral neurons follows cervical tractotomy while reversible chromatolytic alterations occur after thoracic lesions, glucose utilization did not differ in the red nucleus of operated and control rats. However, glucose utilization increased slightly in the inferior colliculus of all operated animals, a finding of indeterminate significance. The failure of axotomized intrinsic neurons of red nucleus and their surround to show altered glucose utilization stands in sharp contrast to the marked increase which occurs in cranial nerve nuclei after axotomy of their contained extrinsic neurons. The data are held to constitute another indication that there is a fundamental difference in the metabolic responses of extrinsic and intrinsic mammalian neurons to axotomy and may support the contention that, in mammals, the axon reaction of intrinsic neurons is fundamentally different from that of extrinsic nerve cells. This difference may have significance for failure of axon regeneration in mammalian CNS.(ABSTRACT TRUNCATED AT 250 WORDS)