Morphometric and histological analysis of the superior cervical ganglion in experimental Chagas' disease in rats.

Histological methods were used for studying the left superior cervical ganglia of control and T. cruzi infected female rats killed 13, 20, and 34 days after inoculation. Concomitantly, the sympathetic innervation of the heart auricular appendages and of the submandibular gland was studied by a glyoxylic acid-induced fluorescence method for catecholamines. At day 34 of infection, the superior cervical ganglia of an additional group of control and infected animals were studied morphometrically through the determination of ganglion volume, total number, and nuclear diameter of the principal neurons. No amastigote pseudocyst could be detected inside the ganglia at any time during infection. Inflammatory reactions were very discrete or absent at day 13 of infection, but were clearly present at day 20 as periganglionitis (in all infected animals) or ganglionitis (in 62.5% of the infected animals). These reactions again became very discrete at day 34 of infection. None of the morphometric parameters analyzed were altered by Chagas' disease. Histochemical studies on the sympathetic innervation of the heart and submandibular gland showed disappearance or rarefaction of fluorescent nerve fibers, starting around the 13th day of infection. The involvement of sympathetic nerve terminals in Chagas' disease is a local phenomenon rather than a consequence of parasitism or destruction.