Neurotoxicity induced by a single oral dose of aniline in rats

The neurotoxicity of aniline and its age-dependent responses were investiga ted in male rats. Groups of 6 rats, 4-week-old, were treated once with anil ine (500, 750 or 1,000 mg/kg) or olive oil by gavage. Additional groups of 6 rats, 7- or 10-week-old, were treated once with 800 mg/kg of aniline or o live oil. Paralytic gait or hindlimb paralysis was observed between post-tr eatment days 8 and 15 in two out of six rats receiving 1,000 mg/kg of anili ne at 4 weeks of age. On post-treatment day 15, spongy change in the white matter of the spinal cord was observed in all rats receiving 750 or 1,000 m g/kg of aniline at 4 weeks of age. The lateral and ventral columns of the t horacic spinal cord were the most severely affected. Spongy change in the f acial nerve and spinal trigeminal tracts of pens and medulla oblongata, and mild degeneration of the peripheral nerves was found in 3 out of 6 rats re ceiving 1,000 mg/kg of aniline. At the ultrastructural level, the spongy ch ange was due to distention of the myelin sheath and splitting of the intrap eriod line. Axons were well preserved in the affected nerve fibers. No abno rmalities were seen in the neuronal cell bodies. Although transient cyanosi s was observed in all rats receiving 800 mg/kg of aniline at 7- or 10-week- old, as well as in rats receiving 750 or 1,000 mg/kg of aniline at 4-week-o ld, no treatment-related neurobehavioral or morphologic abnormalities were found in the former. These findings demonstrate the neurotoxicity of orally administered aniline for rats, depending upon the age of the animal at the time of administration.