African trypanosomiasis in the rat alters melatonin secretion and melatonin receptor binding in the suprachiasmatic nucleus

Rats infected with Trypanosoma brucei brucei, a subspecies of the extracell ular parasites that cause African sleeping sickness, were examined for dist urbances in the circadian rhythms of melatonin secretion (evaluated by dete rmination of the excretion of melatonin in the urine) and the binding of me latonin to its receptor in the suprachiasmatic nuclei of the anterior hypot halamus, In normal and infected rats, Cosinor analysis showed a significant nocturnal peak. The amplitude of this peak was, however, significantly dec reased in the infected rats. The peak of melatonin receptor binding in the suprachiasmatic nuclei showed a 4-h phase advance in the infected rats, com pared with the controls (0400 and 0800, respectively). These data point to a disturbance in the circadian rhythm of the melatonin-generating systems i n the pathogenesis of African sleeping sickness. (C) 1998 Elsevier Science Inc.