Correlation of the onset of experimental autoimmune encephalomyelitis-like clinical signs with oedema of the spinal cord in tunicamycin-poisoned rats

The neurological signs induced by injection of tunicamycin are, in young adult rats, virtually identical to those typical of acute experimental autoimmune encephalomyelitis (EAE). Vasogenic exudation, of which the occurrence in the spinal cord of EAE rats has been shown to coincide with the onset of clinical signs, was investigated by quantitative electroimmunoblotting of central nervous system (CNS) tissue at various times following tunicamycin injection of young adult rats. Highly elevated levels of extravasated plasma proteins were observed in the spinal cord from 48 h after injection and, as in EAE rats, these increases coincided with the onset of neurological impairment. At 72 h post-injection, significant increases were also found in the brain of affected animals, albeit at much reduced levels. This is in contrast to previously reported findings in nursling rats where oedema was shown to be predominantly located in the brain. Quantitative electroimmunoblotting for myelin basic protein (MBP) in the CNS of tunicamycin-treated young adult rats indicated that, as in acute EAE, no extensive demyelination had occurred. These data provided further evidence that in both neurological diseases, vasogenic oedema of the spinal cord may be causally related to the appearance of neurological signs and suggested that its differential localization in the CNS may lead to differential neurological impairment.