AXOTOMY INDUCES NADPH DIAPHORASE ACTIVITY IN NEONATAL BUT NOT ADULT MOTONEURONS

RAT sciatic motoneurones do not normally express NADPH diaphorase acti vity. However, after cutting the sciatic nerve in the mid-thigh of neo nates and applying the retrograde tracer fast blue, such reactivity wa s found colocalized with fast blue in about one-fifth of sciatic moton eurones 4 days following the lesion. This proportion of sciatic motone urones expressing NADPH diaphorase activity remained approximately con stant for 14 days after axotomy during which time extensive motoneuron e death occurred. Many NADPH diaphorase-positive motoneurones appeared shrunken with degenerative changes to the nucleus. In contrast, the s ame lesion in adult animals failed to induce any reactivity or cause m otoneurone death 4-28 days after axotomy. Induction of nitric oxide sy nthesising capability may play a role in the death of target-deprived immature motoneurones.