Fig. 3.

Lower (A) and higher (B–D) magnification of light photomicrographs showing cytochrome oxidase (COX) reactivity in the suprachiasmatic nucleus (SCN) of normal untreated (A,B) and total sleep-deprived (C,D) rats. In normal untreated rats (A,B), numerous moderate to strong COX-reactive neurons were identified in the SCN. However, following 5 days of total sleep deprivation (TSD) (C,D), only a few neurons with weak COX staining intensity were detected (C,D). Also note that the reduction of COX expression was evident in both groups at different sample time-points (C,D). D, day; N, night; V, third ventricle; op, optic chiasma; Scale bar = 400 μm in (A) and 200 μm in (B–D).