Alpha-interferon modifies cortical EEG activity: dose-dependence and antagonism by naloxone

Activation of the immune system is believed to provide signals in the form of chemical messengers that are able to change neural activity in a variety of regions of the central nervous system. In studies designed to examine the effects of alpha-interferon (alpha-IFN) upon the central nervous system, recordings of cortical EEG were made following intracerebroventricular injection of various doses of the cytokine. Administration of 25 U of alpha-IFN increased the amount of wake and decreased the amount of desynchronized sleep in the first hour following injection; an increase in synchronization being seen in the third hour. alpha-IFN at 250 U increased the amount of synchronization and decreased the amount of desynchronized sleep in the EEG, principally in the second hour, with 2,500 U having similar but more potent effects, mostly in the first hour. The (mu) opiate receptor antagonist, naloxone, was found to decrease the amount of EEG synchronization and blocked the increases in synchronized sleep produced by 250 U alpha-IFN. The data suggest that alpha-interferon increases EEG synchronization in a dose-dependent and specific manner, probably via central mu-opiate receptors. The increased wake in the EEG following 25 U suggests, however, that another discrete effect of alpha-IFN may also exist.