Naloxone antagonizes behavioural and ECoG effects induced by systemic or intracerebral administration of some lymphokines.

Rat interferon, alpha-interferon, interleukin-2 and recombinant interleukin-2 microinjected into the third cerebral ventricle produced in rats typical behavioural sedation and/or sleep and ECoG synchronization while beta-interferon produced no behavioural sleep and ECoG synchronization. A slight sedation was observed after highest dose of beta-interferon only. During sleep induced by these lymphokines a dose-dependent increase in total voltage power as well as in the 0.5-3, 4-7 and 12-16 Hz frequency bands was observed. Much lower doses were required to produce similar behavioural and ECoG spectrum power effects after microinfusion of interferons and interleukin-2 into the locus coeruleus. No significant behavioural and ECoG changes were obtained after microinfusion of the same doses of interferons and interleukin-2 into other areas of the brain (caudate nucleus, dorsal hippocampus, substantia nigra-pars compacta-, ventromedial hypothalamus). The behavioural and ECoG effects of alpha-interferon, rat interferon and interleukin-2 were blocked in animals pretreated with naloxone. These results are consistent with the hypothesis that the behavioural and ECoG effects of these lymphokines are mediated at locus coeruleus level via a stimulation of opiate receptors.