The 21-aminosteroid U-74389F attenuates hyperexpression of GAP-43 and NADPH-diaphorase in the spinal cord of wobbler mouse, a model for amyotrophic lateral sclerosis

The wobbler mouse suffers an autosomal recessive mutation producing severe neurodegeneration and astrogliosis in spinal cord. It has been considered a model for amyotrophic lateral sclerosis. We have studied in these animals the expression of two proteins, the growth-associated protein (GAP-43) and the NADPH-diaphorase, the nitric oxide synthesizing enzyme, employing immun ocytochemistry and histochemistry. We found higher expression of GAP-43 imm unoreactivity in dorsal hem, Lamina X, corticospinal tract and ventral horn motoneurons in wobbler mice compared to controls. Weak NADPH-diaphorase ac tivity was present in control motoneurons, in contrast to intense labeling of the wobbler group. No differences in diaphorase activity was measured in the rest of the spinal cord between control and mutant mice. A group of an imals received subcutaneously for 4 days a 50 mg pellet of U-74389F, a gluc ocorticoid-derived 21-aminosteroid with antioxidant properties but without glucocorticoid activity. U-74389F slightly attenuated GAP-43 immunostaining in dorsal regions of the spinal cord from wobblers but not in controls. Ho wever, in motoneurons of wobbler mice number of GAP-43 immunopositive neuro ns, cell processes and reaction intensity were reduced by U-74389F. The ami nosteroid reduced by 50% motoneuron NADPH-diaphorase activity. Hyperexpress ion of GAP-43 immunoreactivity in wobbler mice may represent an exaggerated neuronal response to advancing degeneration or muscle denervation. It may also be linked to increased nitric oxide levels. U-74389F may stop neurodeg eneration and/or increase muscle trophism and stop oxidative stress, conseq uently GAP-43 hyperexpression was attenuated. Wobbler mice may be important models to evaluate the use of antioxidant steroid therapy with a view to i ts use in human motoneuron disease.