Enzyme histochemical profile of immunohistochemically identified Renshaw cells in rat lumbar spinal cord

Activity levels of cytochrome oxidase, acid phosphatase, and NADPH diaphora se were examined in the perikarya of immunohistochemically identified Rensh aw cells from sections of rat lumbar spinal cord, Renshaw cell profiles wer e identified on the basis of their characteristic anti-gephyrin-immunofluor escent labelling. Intrasomatic densities of enzyme histochemical reaction p roduct were employed as indicators of relative mitochondrial activity (cyto chrome oxidase), intracytoplasmic digestion (acid phosphatase), or putative nitrergic signalling (NAPDH-diaphorase). Approximately half of the Renshaw cell somata examined displayed moderate levels of cytochrome oxidase react ion product (142 of 262 Renshaw cells) or low levels of acid phosphatase ac tivity (156 of 243 Renshaw cells), A majority (160 of 202 cells) of Renshaw cells contained low intrasomatic levels of NADPH-diaphorase activity but m ost of these cells were closely apposed by at least one NADPH-diaphorase re active axonal varicosity, Our findings suggest that moderate levels of peri karyal oxidative metabolism and low levels of intracytoplasmic digestion ar e sufficient for, and support, the unique physiological capabilities of Ren shaw cells, The presence of NADPH-diaphorase containing somatic close conta cts indicate that nitric oxide may have at least a minor role in the regula tion of Renshaw cell activity. These results are complementary and consiste nt with previous morphological and pharmacological demonstrations of Rensha w cell heterogeneity, (C) 2001 Elsevier Science Inc.