THE EFFECT OF GONADECTOMY ON THE CLINICAL COURSE OF CHRONIC EXPERIMENTAL ALLERGIC ENCEPHALOMYELITIS

Experimental allergic encephalomyelitis (EAE) is an animal model for t he human neurological disease multiple sclerosis (MS). Upon immunizati on with guinea pig spinal cord under a low dose of Cyclosporin A, male Lewis rats develop a severe chronic (relapsing) course of EAE (CR-EAE ). By contrast, female Lewis rats develop a more mitigated course of E AE: only half of the female rats develop relapses. To Further analyze factors determining this sexual dimorphism in the course of EAE, in th e present study male and female Lewis rats were gonadectomized before induction of CR-EAE. Now both male and female rats all developed a sev ere chronic course of EAE, showing extensive pathological changes in t he CNS. In the female sham-gonadectomy (control) group only one third of the rats developed relapses. These female rats only showed mild pat hological changes in the CNS. In the male sham-gonadectomy (control) g roup all rats developed relapses of EAE and showed extensive pathologi cal changes in the CNS. From these data we conclude that the presence of the ovaries (partially) protects female rats against relapses of EA E and CNS injury. Presence or absence of the testes apparently makes n o difference on the course of EAE. We propose that sex hormones produc ed in the ovaries protect female rats against relapses of EAE and unde rlying CNS injury.