Heart autonomic innervation during the acute phase of experimental American trypanosomiasis in the dog.

Abstract

Heart autonomic innervation was studied in dogs during the acute phase of the experimental infection with the Berenice-78 strain of Trypanosoma cruzi. A glyoxylic acid-induced fluorescence method for catecholamines and a thiocholine method for demonstrating acetylcholinesterase activity showed the sympathetic and the parasympathetic nerve fibers, respectively. At day 34 of infection, moderate-to-intense rarefaction of both cholinergic and noradrenergic nerve fibers occurred in the atria of all animals coincident with moderate to intense myocarditis. In the ventricles, sympathetic denervation was clearly present only when the inflammatory processes were moderate to intense. Preliminary results on the chronic phase indicate that normal autonomic innervation coexists with an incipient chronic fibrosing myocarditis.

Pathology of intracardiac nerves in experimental Chagas disease

“…The possibility of disappearance or even the occurrence of partial destruction of intracardiac nerves could not be demonstrated, neither by morphometric means in sections histochemically prepared for parasympathetic nerves, nor by electron microscopy. Therefore, present data are in marked contrast with the reported findings of severe destruction of nerves followed by extensive regeneration observed in rats (Machado et al 1979(Machado et al , 1987 and dogs (Machado et al 1998) with T. cruzi infection. Actually, the Machado's group demonstrated neither destruction, nor regeneration of cardiac nerves, but disappearance and re-appearance of enzymatic reactivity in acute and chronic Chagas myocarditis, respectively, in rats and dogs.…”

“…So far, only one group of investigators have devoted a series of papers to this subject (Machado et al 1975(Machado et al , 1978(Machado et al , 1979(Machado et al , 1987(Machado et al , 1998. These papers, mainly based on histological findings, described severe, diffuse and focal, destructive cardiac neural lesions affecting both the sympathetic and parasympathetic fibers of the heart, during acute Chagas myocarditis in rats and dogs.…”

Chagas' heart disease

“…These findings were reproduced by investigations in animal models of the disease 49,[83][84][85][86][96][97][98][99] . The histopathologic features are foci of damaged nervous tissue arranged in a diffuse and irregular distribution.…”

Impaired autonomic control of heart interval changes to Valsalva manoeuvre in Chagas' disease without overt manifestation

“…The human and experimental indeterminate forms present less conspicuous lesions of cardiac intrinsic innervation, which are usually represented by discrete to moderate focal or zonal chronic neuroganglionitis (Lopes and Tafuri, 1983;Andrade, 1984;Oliveira, 1985;Chapadeiro et al, 1991). Cardiac autonomic damage has also been observed in acute and chronic experimental Trypanosoma cruzi infection in mice (Tafuri, 1970;Souza et al, 1996), dogs (Andrade, 1984;Machado et al, 1998), rats (Chapadeiro et al, 1991;Junqueira et al, 1992), and hamsters (Chapadeiro et al, 1999) among other animal models.…”