Cytochrome oxidase activity as a marker for periodontal sensory receptors in the rat

Abstract

Cytochrome oxidase activity was explored histochemically in axon terminals of periodontal Ruffini endings of rat upper incisors at both the light- and electron-microscopic levels. Staining clearly demonstrated ramified structures in the alveolar half of the periodontal ligament. These structures resembled the profiles of the axon terminals of the periodontal Ruffini ending previously demonstrated by an immunohistochemical method for neurofilament protein. Histochemically at the electronmicroscopic level, the ramified structures were identified as true Ruffini endings in which each axon terminal was filled with reactive mitochondria. Two types of mitochondria were distinguished with respect to the localization pattern of reaction products; almost all mitochondria were positive for cytochrome oxidase activity, with only a few negative. As the enzyme activity did not decrease after demineralization, the findings suggest that cytochrome oxidase is a useful marker enzyme for demonstrating sensory receptors in the periodontal ligament. Histochemical methods for cytochrome oxidase may contribute to the light- and electron-microscopic morphological analysis of periodontal sensory receptors.