INSULAR CORTEX LESIONS IMPAIR THE ACQUISITION OF CONDITIONED IMMUNOSUPPRESSION

Conditioned immunosuppression can be readily obtained in animals by as sociating a taste with an immunosuppressive drug. On subsequent exposu re to the conditioned taste, the animals show an attenuated immune res ponse and also exhibit a conditioned taste aversion. It has been estab lished that insular cortex lesions disrupt the acquisition of conditio ned taste aversion. The effect of NMDA-induced lesions in either the i nsular cortex or the parietal cortex of male Wistar rats was evaluated in the acquisition of conditioned immunosuppression in two experiment s. Unlesioned control rats showed the conditioned immunosuppressive re sponse after reexposure to the taste, as indicated by lower hemaggluti nating titers to sheep red blood cells in the first experiment and by a decreased IgM production to ovalbumin, measured by ELISA, in the sec ond experiment. Insular cortex-lesioned rats did not show the conditio ned immunosuppression in either experiment, while parietal cortex lesi ons and the sham-lesioned animals presented a clear decrease of hemagg lutinating titer and a low IgM production. The insular cortex lesions did not affect the normal immune response, showing normal hemagglutina ting titers and IgM production when compared to nonconditioned control s. The immunosuppressive action of cyclophosphamide also remained unal tered. In conclusion, these results show that the insular cortex is es sential for the acquisition of conditioned immunosuppression. (C) 1996 Academic Press, Inc.