EFFECTS OF TRYPANOSOMA BRUCEI BRUCEI INFECTION ON THE HISTOLOGY AND FUNCTIONING OF THE HYPOTHALAMO-THALAMUS-PINEAL GLAND AXIS IN MALE ALBINO RATS (Rattus novergicus)

Abstract

Trypanosomosis is a major health problem threatening the lives of over 60 million people in 37 countries in sub-Saharan Africa. It is caused by Trypanosoma parasites which are transmitted through a bite of an infected tsetse fly of the genus Glossina. The disease is characterized by sleep/wake disturbances, and disruptions in other circadian rhythm activities like body temperature and hormone secretion. Since histopathological studies on brain regions involved in the control of circadian rhythms are scanty, this study investigated the effects of T.b. brucei infection on the hypothalamic suprachiasmatic and paraventricular nuclei, thalamic lateral geniculate nucleus, anterior pituitary and pineal glands in albino rats. It also investigated the effects of T.b. brucei infection on plasma concentration of melatonin and adrenocorticotropic hormone (ACTH). Twelve control and twelve experimental male albino rats, aged 3-3½ months, were used in this study. Body weight and temperature of each rat was measured four days in a week. The experimental rats were injected intraperitoneally with 0.2ml of infected blood containing 1 x 104 live T.b. brucei parasites. Once a week, 1ml of blood was obtained from the tail of each rat and the concentration of melatonin and ACTH in the plasma determined using an automated immunoanalyzer. The infected animals were allowed to go through the full course of infection, without treatment, and sacrificed when they were in extremis. For every experimental rat sacrificed, a control rat was sacrificed. Each rat was anaesthetized, decapitated, and the brain immediately extracted from the skull. The brain was fixed in neutral buffered formalin for at least 48 hours. The anterior pituitary and pineal glands were later extracted from the brain and a coronal section of the brain made. These tissues were processed histologically and stained using the haematoxylin and eosin method. The stained slides were examined under a microscope and photomicrographs taken. Parasites were detected in the blood of experimental rats 5-8 days post-infection. Significant differences in body weight (p = 0.0114), temperature (p = 0.0113), and plasma concentration of melatonin (p = 0.0382) and ACTH (p = 0.0190), were recorded between the control and experimental rats. Histopathological changes, including tissue degeneration and infiltration and proliferation of glial cells, were observed in the suprachiasmatic nucleus, paraventricular nucleus, lateral geniculate nucleus, anterior pituitary gland, and pineal gland of infected rats. These findings provide a basis for understanding the physiological and behavioural changes that characterize trypanosomosis