Lateral geniculate nucleus histopathology in the rat experimental model of African trypanosomosis

Abstract

Trypanosomosis is an infectious disease of humans and animals characterized by sleep/wake disturbances and disruptions in other circadian rhythm activities. The disease is caused by protozoan parasites of the genus Trypanosoma and transmitted by the bite of infected tsetse flies of the Glossina species. Although trypanosomosis has a well knownaetiology, histopathological studies on brain regions involved in the control of circadian rhythms are scanty. Lateral geniculate nucleus works in conjunction with the suprachiasmatic nucleus, the master circadian rhythm pacemaker, in regulating circadian rhythms. The purpose of this study was to investigate the effect of T.b.brucei infection on the histology of the lateral geniculate nucleus, a brain region that can serve as an alternative secondary circadian rhythm pacemaker when the master pacemaker fails. Twelve control and twelve experimental male albino rats were used in this study. The experimental rats were inoculated intraperitoneally with 0.2ml of infected blood containing 1 x 104T.b.bruceiparasites. The infected animals were allowed to go through the full course of infection and sacrificed when they were in extremis. Each rat was decapitated and the brain immediately extracted from the skull. The brain was fixed in 10% buffered neutral formalin for at least 48 hours. The brain was later removed from the formalin solution and a coronal section made. The coronal section was processed histologically and stained using the haematoxylin and eosin method. The stained slides were observed under a microscope and photomicrographs taken. Histological alterations, including tissue degeneration, infiltration and proliferation of cells, and perivascular cuffing were observed in the lateral geniculate nucleus of infected rats. Lateral geniculate nucleus cannot, therefore, serve as an alternative secondary circadian rhythm pacemaker during trypanosome infection.

Keywords: Trypanosomosis, Lateral geniculate nucleus, Histopathology, Circadian rhythm