CHANGES OF CYTOCHROME-OXIDASE ACTIVITY IN RAT SUPRACHIASMATIC NUCLEUS

This paper evaluates the changes of cytochrome oxidase (CO) activity t hat take place in the suprachiasmatic nucleus (SCN) during the light-d ark cycle. CO is a mitochondrial energy-generating enzyme used as a ma rker of neural oxidative metabolism. We measured CO activity using qua ntitative histochemistry calibrated with brain tissue standards and a computerized analysis image system. The results indicate that the CO e nzyme activity changes on the basis of a circadian pattern, with the h igher levels during the light phase (P < 0.0001). These changes are de tected over a period of hours, in accordance with other studies on the possible shea-term regulation of CO activity in the nervous system. I t is, therefore, possible to apply this methodology to the study of th e SCN and other brain areas which show functional rhythmicity. (C) 199 7 Elsevier Science B.V.