TRYPANOSOMES CAUSE DYSREGULATION OF C-FOS EXPRESSION IN THE RAT SUPRACHIASMATIC NUCLEUS

RATS infected with the parasite Trypanosoma brucei brucei showed selec tive changes of c-fos expression in the suprachiasmatic nucleus of the hypothalamus (SCN) during spontaneous sleep (S) and wakefulness (W) u nder a basal 12 h/12 h light-dark (L-D) cycle. In the vast majority of W (D phase) control animals the SCN was devoid of cells displaying Fo s-related immunopositivity, while Fos-like-immunoreactive (ir) neurone s were detected in most S (L phase) control rats. In most infected ani mals, on the other hand, Fos-ir neurones were detected in the SCN duri ng W, but not during the S period, with a significant difference betwe en control and infected S rats. Thus, these data indicate that the bas al c-fos expression in the SCN during the L-D and S-W cycles is consid erably altered in experimental trypanosomiasis. This is the first obse rvation of a selective change in the SCN in trypanosome-infected rat b rains. Since the SCN plays an important role as a pacemaker for biolog ical rhythms, this finding may provide a basis for understanding the p athogenesis behind endogenous rhythm dysregulation and changes in slee ping pattern in human trypanosomiasis (African sleeping sickness).