DIFFERENTIAL-EFFECTS OF NMDA-INDUCED LESIONS INTO THE INSULAR CORTEX AND AMYGDALA ON THE ACQUISITION AND EVOCATION OF CONDITIONED IMMUNOSUPPRESSION

It has been established that the insular cortex (IC) mediates conditio ned taste aversion, and recently we have demonstrated that lesions of this structure disrupt the acquisition of conditioned immunosuppressio n (CIS). The IC is functionally and reciprocally interconnected with t he amygdala (AM) which has been suggested to be involved in neural-imm une interactions. The aim of this work was to test the effects of NMDA -induced lesions in either the IC or AM in the acquisition (lesions ma de before conditioning) and evocation (lesions made after conditioning ) of a conditioned immunosuppression task, obtained by one single pair ing of saccharin taste and the immunosuppressive drug, cyclophosphamid e. AM and IC lesioned rats were separated into four groups: the first two received lesions before and the other two were lesioned after the acquisition of conditioned immunosuppression. Twenty days after condit ioning, animals were reexposed to saccharin and immunized with ovalbum in. After immunization, blood samples were taken, and analyzed by ELIS A. The results showed that IC lesions disrupted the acquisition and ev ocation of CTA and CIS. Conversely, AM lesions disrupted only the acqu isition of CIS. These data suggest that the IC is involved in the neur al mechanisms underlying the acquisition and evocation of conditioned immunosuppression, and the amygdala could be important in mediating th e input of the immune information necessary for the acquisition of con ditioned immunosuppression. (C) 1998 Academic Press.