Cardiac denervation in mice infected with Trypanosoma cruzi.

The neuronal features of the hearts of mice that were acutely or chronically infected with the Y strain of Trypanosoma cruzi were compared with those of control hearts from uninfected mice. Whole-mount preparations of the murine atria, isolated by microdissection, were stained to reveal neurons with NADH-diaphorase activity. Counts, by a microscopist who was blind to the infection status of the donor mouse, revealed that there were significantly (38%) fewer such neurons in the atria from the acutely infected mice than in the atria from the control hearts. The ganglia of the infected mice were also irregularly distributed, severely damaged ganglia being found beside slightly degenerated or morphologically normal ones. Although the ganglia contained small, medium and large neurons, the apparent destruction caused by T. cruzi was confined to the large ones. As neuron counts in preparations of hearts from mice with chronic infections were 32% lower than those in the control hearts, there appears to be no additional loss of cardiac neurons as the acute infection in mice progresses to the chronic phase.