COMPARISON BETWEEN THE EARLY CHANGES IN ISONIAZID INTOXICATION AND THE CHROMATOLYTIC RESPONSE TO NERVE LIGATION IN SPINAL GANGLION CELLS OF THE RAT

Abstract

The early effects of acute isoniazid [INH] intoxication and the early responses of the neuron to axotomy were compared in lumbar spinal ganglion cells in the rat. The cells were studied by light microscopy and EM during the 4 days after a single oral dose (2 g/kg) is isoniazid and for 4 days after application of a tight ligature to the sciatic nerve at the level of the sciatic notch. After axotomy a greater proportion of cells showed changes visible by light microscopy and EM than after INH. Small dark neurons were affected more rapidly and more severely by both insults than the large light cells, as evidenced principally by changes in their ribosomal organization. Large light cells showed little response to INH. The 1st response to axotomy was visible .apprx. 12 h after injury. The response to INH began 24 h after the single oral dose. The early cell responses to INH therefore apparently precede axon degeneration which is first seen 72 h later and are probably a direct toxic effect.