Severity of experimental allergic encephalomyelitis in rats depends upon the temporal contiguity between limbic seizures and inoculation.

Limbic seizures (forepaw clonus) were induced in Lewis rats by subcutaneous injections of lithium (3 mEq/kg) followed 24 h later by a muscarinic agent. Either 7 days before, 7 days after, or on the day of seizures, rats were inoculated with a spinal cord preparation. Other groups received these preparations but served as treatment (no seizure) controls. In three separate experiments, rats in which seizures had been induced at the time of inoculation displayed significant increases in the severity of clinical symptoms 14-20 days later relative to controls while rats in which seizures had been induced 7 days after inoculation displayed less severe symptoms; the latter effect was partially simulated by multiple injections of 1 mg/kg dexamethasone. The immunofacilitation effect was much stronger than the immunosuppression and explained 25-30% of the variance in the clinical severity scores.