Background: Mercury is a toxic element which for the first time its toxic effects were observed in newborns in Minimata (Japan) and it was called as Minimata syndrome. Signs of exposure include tremor, ataxia and paralysis. The regulation of cardiac function is dependent on cardiac ganglia which consisted of small cluster of schwann cells, nerve cells and fibers. In this study the morphology of schwann cells and nerve fibers of rabbit cardiac ganglia were studied after methyl mercury administration.

Materials and Methods: Twenty male White New Zealand rabbits were equally divided into the control and experimental groups. The experimental group was given a daily intraperitoneal injection of a single dose of 4 mg/kg methyl mercury dissolved in distilled water for two weeks. The control group received only distilled water. At the end of the injection period, the two groups were anesthetized and perfused with Karnovsky solution. The atrial and ventricular fat pads were excised and fixed in Karnovsky solution. The ganglia were separated from the fat pads under the stereomicroscope and processed for EM.

Results: The TEM observations showed that some schwann cells contained vacuoles in the cytoplasm and condensed chromatin in nucleus. The inclusion bodies were observed among the myelin layers of the nerve fibers. These results revealed that methyl mercury induces neuropathy in rabbit cardiac ganglia.

Conclusion: The schwann cells and the myelin sheath of the nerve fibers in the rabbit cardiac ganglia undergoes degenerative changes after methyl mercury administration and the long term consequences of pathological changes affecting the ability of the ganglia.