Electrophysiological and histopathological evaluation of respiratory tract, diaphragm, and phrenic nerve after dichlorvos inhalation in rats

The aim of this study was to investigate the dose-related effects of dichlorvos inhalation on electrophysiological alterations of diaphragm and phrenic nerve and the changes in the histologic structure of respiratory system. This study was performed on 33 rats divided into 5 groups, inhaling 1, 2, 5, 10, and 15 mug/L of dichlorvos, respectively. Electrodiagnostic investigations of diaphragm and phrenic nerve were made before and after inhalations. Aspiration samples were taken from lungs to evaluate the presence of infection agents. The airways, lungs, and diaphragms were dissected out for histologic investigation. Rats exposed to a low concentration of dichlorvos (1-5 mug/L) showed no symptoms of intoxication, but exposure to higher doses (10-15 mug/L) induced dyspnea in several animals. Lower doses of dichlorvos revealed no electromyographic changes on diaphragm, whereas higher doses revealed a clear neuropathic involvement. Delayed phrenic nerve motor conduction velocity was noted for each group (p<.05). Morphologic changes on the tracheal epithelium, hyperplasia, thickening of the blood-air barrier, degeneration in alveoli, and ductus alveolaris were seen in histopathologic investigation. In conclusion, the acute inhalation of dichlorvos caused clear evidence of neuropathic involvement of the diaphragm and the phrenic nerve. Also, toxic pneumonitis and injury to the tracheal epithelial were noticed.