DYSREGULATION OF PHOTIC INDUCTION OF FOS-RELATED PROTEIN IN THE BIOLOGICAL CLOCK DURING EXPERIMENTAL TRYPANOSOMIASIS

The mammalian suprachiasmatic nuclei of the hypothalamus (SCN) serve a s pacemaker for circadian rhythms and the immediate-early gene c-fos i s known to be induced by photic stimulation in the SCN of rodents. We studied the induction of Fos-related protein following a light pulse i n rats infected with Trypanosoma brucei. This parasite causes in human s African sleeping sickness, a neuropsychiatric syndrome that involves changes of endogenous biological rhythms. Fos-like immunoreactivity a fter photic stimulation was dramatically reduced in the SCN of trypano some- infected rats during the subjective night. These findings indica te that the photic entrainment of the biological dock may be altered d uring the infection.