Abstract
Toxoplasmosis, a disease caused by Toxoplasma gondii, is an important health problem, especially in immunocompromised hosts. T. gondii uses the gut wall as an infection gateway, with tropism for muscular and nervous tissues causing intestinal alterations, including some in the enteric nervous system. This study aims at investigating the colon of rats infected by T. gondii in order to understand how the amount of oocysts influences in myenteric neuronal changes. Sixty Wistar rats (Rattus norvegicus) were divided into six groups. One group remained as a control and the others received inocula of 10, 50, 100, 500 or 5,000 oocysts of T. gondii. The animals were euthanized after 30 days of infection. The total neuronal population and the nitrergic subpopulation in the colon myenteric plexus of each animal was counted. The data were statistically analyzed showing less weight gain in rats with 10, 500 and 5,000 oocysts. A decrease in the number of total neurons with 50, 100 or 5,000 oocysts and an increase in the nitrergic population with 10, 100, 500 or 5,000 oocysts were verified. These results show that neuronal alterations are more significant when the infection is induced by larger inocula and reinforces the suspicion that neuronal loss is directed at cholinergic neurons.
Highlights
Toxoplasma gondii is an obligate intracellular coccidian protozoan parasite, which is widely distributed (WEISS & KIM, 2007)
This study aims at investigating the colon of rats infected by T. gondii in order to understand how the amount of oocysts influences in myenteric neuronal changes
A comparison of the number of myenteric neurons of each animal in the infected groups and the average number presented by the control group (CG) and its confidence interval by both techniques indicated that 83% of the animals in G100 and 86% in G5000 presented neuronal loss
Summary
Toxoplasma gondii is an obligate intracellular coccidian protozoan parasite, which is widely distributed (WEISS & KIM, 2007). The type I strain is considered of high virulence, type II is of intermediate virulence and type III is of low virulence (SILVA et al, 2005; FREYRE et al, 2001). The strain used in this study, identified as ME49 (genotype II), was isolated, in the northern hemisphere, from the muscles of a ram (LUNDE & JACOBS, 1983), and the fact that it is not of high virulence favors its use in studies of the chronic phase of the infection (MAUBON et al, 2008)
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