Sleep fragmentation, and changes in locomotor activity and body temperature in trypanosome-infected rats

The rest-activity and body temperature 24 h cycles, as well as the structure of spontaneous sleep, were studied in rats 3 weeks after infection with monomorphic Trypanosoma brucei brucei. This parasite belongs to the species of trypanosomes that causes in humans African sleeping sickness, a neuropsychiatric syndrome that involves alterations of endogenous biological rhythms. In the infected rats, entrained to a 12 h:12 h photoperiod, a considerable hypokinesia was detected during the hours of darkness. A significant oscillation of the body temperature during 24 h was lost in some infected animals. In the other infected animals, the body temperature cycle displayed a lower amplitude and a phase advance. The mean temperature was slightly higher in the infected than in control rats during the period of light. A detailed analysis of the structure of spontaneous sleep, based on daytime electroencephalographic recordings, revealed during trypanosome infection an increased relative proportion of wake, and a decreased percent value of synchronized sleep. A marked reduction of the mean REM latency and a fragmented pattern of synchronized sleep, resulting in a considerable alteration of the REM-non-REM sleep sequences, were also observed in the infected animals. These findings indicate that trypanosomiasis in the rat results in a striking sleep fragmentation, as well as in changes of locomotor activity and body temperature rhythm. Thus, trypanosome infection in the rat provides an experimental model of sleep dysregulation in a structurally intact brain, and may provide an animal model of endogenous rhythm changes documented in African sleeping sickness.