Lesion-induced neuronal nitric oxide synthase in Purkinje cells of the rat cerebellar cortex: Histochemical and in situ hybridization study

Lesion-induced induction of neuronal nitric oxide synthase (nNOS) was examined in the rat cerebellum. The stab-lesioned cerebellar cortex was examined with NADPH-diaphorase (NADPH-d) histochemistry and in situ hybridization using nNOS cRNA probe at 1, 3, 7, 14, 35 days post-lesion. NADPH-d- and nNOS mRNA-positive Purkinje cells appeared adjacent to the lesion by 3 days after the lesion. The area of distribution expanded and the number of positive cells increased at 7 days after the lesion, and at 14 days post-lesion, shrunken NADPH-d-positive Purkinje cells with irregular surface appeared. NADPH-d activity and nNOS mRNA signal could not be detected in Purkinje cells after 35 days post-lesion. Combined NADPH-d histochemistory and in situ hybridization using glutamic acid decarboxylase (GAD) cRNA probe revealed that nNOS-expressing Purkinje cells showed fewer GAD mRNA signals than those in normal Purkinje cells. The atrophic contour and the lower expression of GAD mRNA signals in NADPH-d positive Purkinje cells suggest that nNOS is expressed under a degenerating process.