Objective To observe the microstructure of the
substantia nigra of mice chronically intoxicated with Cd.Methods Light microscopy
and trasmission electorn microscopy were used.The TH-positive neurons in the
substantia nigra were analyzed with morphometric technique.Results (1)Most neurons were degenerated.The nuclei appeared pycnosis and deformation.The heterochromatins were increased and migrated to the marginal zone of the nuclei.The nissl bodies(rough surfaced endoplasmic reticulum and free ribosome) and other organelles in the parikaryon obvously were decreased.(2) A few necrotic neurons were found.The nuclear envelopes were broken and the nuclei were dissolved.The Nissl bodies and other organelles in the parikaryon were disappeared.(3)The quantity of dopamine neurons and the dopamine producted by them were decreased.(4)There were the softening focuses in the substantia nigra.The boundary of the focuses were clear.Some neurons were dissolved and some neurons were degenerated in the focuses.(5)The inflammation were seen in the substantia nigra.Numberous limphocytes were appeared in the inflammatory areas.The lymphocytes formed an sheath in the periphery of small blood vessel.These findings indicated that the substantia nigra is a target of chronic Cd toxicity and alterations of the microstructure of the substantia nigra by chronic Cd toxicity(especially the quantity of dopamine neurons and the dopamine producted by them were decreased) are similar to the pathological charateristics of
Parkinson's disease.Conclusion Cadmium would be one of the factors induced Parkinson's disease.