Nitrergic Myenteric Neurons are Spared in Experimental Chagasic Megacolon

Chagas disease is a chronic disorder caused by the Trypanosoma cruzi protozoan. The infection causes alterations to the enteric nervous system such as megaesophagus and megacolon. There is evidence of denervation of myenteric ganglia. The intense parasitism of acute phase affects neuronal integrity but contrasts with the absence of parasites and the discreet inflammatory process of chronic phase, indicating a progressive injury mechanism that needs to be better understood in the megacolons. The potential selectivity of enteric neurons classes affected by the progression of the disease is not yet clear. Nitrergic neurons which co-localize other neurotransmitters represent the most common inhibitory neuron of the ENS. Recently a chronic stage of the Chagas disease was reproduced experimentally in a suitable murine model of megacolon. Considering the limitation of studying human intestine and the controversy on the pattern of nNOS involvement in chagasic megacolon, we decided to assess the nitrergic neurons in the myenteric plexus of mice. We used antibodies against structural protein gene product 9.5 (PGP 9.5) and functional neuronal nitric oxide synthase (n-NOS) at the acute and chronic phase of the disease to quantify myenteric ganglionar neurons in the colon of infected and non-infected mice. We found a reduction in the ganglionar number of neurons detected by anti-protein gene product 9.5 antibodies in colon from mice at the chronic stage. However, the number of nitrergic neurons per ganglia remained unchanged along the acute to phase chronic of the disease. Our findings indicate a long-term preservation of nitregic neurons detrimental to other classes of enteric in our model of experimental Chagas disease. We propose that differential loss of enteric neurons is at least one of the structural substrate for the development of the longterm morphfunctional changes that lead to the megacolon.