Early enzyme histochemical changes following transection of dorsal spinal funiculi

Abstract

Histochemical studies of early changes of lactic dehydrogenase activity were done in transected fasc. gracilis and cuneatus of cats, to elucidate the significance of the proximo-distal increase in this enzyme normally found in the terminal portions of these tracts. A rapid and uniform loss of activity in the distal portion of transected tracts favors the concept that the gradient of enzyme activity in normal tracts results from a flow of axoplasm in the fasc. gracilis at a rate exceeding that of its catabolism, rather than an ability of the terminal portion of the axon to synthetize enzyme. Swellings and enzymatic changes in the stump of the transected axonal fibers suggest an early phase of redistribution of axoplasm in axonal stumps that occurs in both stumps, with a continued damming of axoplasm that occurs only in the proximal stumps. Transection of the sciatic nerve does not affect enzyme activity in the dorsal funiculi.