Plasma melatonin rhythm is maintained in human African trypanosomiasis

In human African trypanosomiasis (sleeping sickness), sleep and wake episodes are sporadically distributed throughout the day and the night. Plasma melatonin, sleep-wakefulness and rectal temperature rhythms were studied in 9 Congolese patients suffering from sleeping sickness compared to 6 healthy controls submitted to the same light/dark regime. The circadian distribution of the sleep-wake cycle was disturbed in relation to the severity of the disease. As controls, patients maintained a very distinct plasma melatonin nyctohemeral rhythm which displayed a significant phase advance (1:08 +/- 0:43 and 2:34 +/- 0:31 mean +/- SD, in patients and controls respectively; p < 0.01, U test), as well as a persistent rectal temperature rhythm (mesor 36.67 +/- 0.29 and 36.74 +/- 0.13 degrees C, amplitude 0.29 +/- 0.16 and 0.32 +/- 0.13 degrees C, acrophase 13:53 +/- 2:47 and 15:32 +/- 0:36 for patients and controls respectively). No alteration of these rhythms was observed after treatment. In African controls we observed plasma melatonin characteristics similar to those of European controls, especially for the onset and the duration of the secretion and the stability of the rhythm, despite a different light/dark regime. The dissociation observed between the 3 rhythms (melatonin, temperature and sleep-wake cycle) is discussed, taking into consideration a functional compartmentalization of the suprachiasmatic nuclei or more likely a disruption of the neural pathway between the circadian clock and structures involved in the regulation of the sleep-wake cycle, related to the activity of compounds released by the parasites or host cells.