Behavioral Symptoms of Anxiety and Depression and Brain Monoamine Contents in Rats after Chronic Intranasal Administration of Interferon-α

Abstract

The effects of chronic (17 days) intranasal administration of low (50 IU/kg) and intermediate (8000 IU/kg) doses of human interferon-α (IA) on behavioral indicators of anxiety and depression and the monoaminergic system of the brain were studied in rats. Control rats received the same volume of intranasal physiological saline. IA was found to have any ambiguous effects on anxiety levels. Thus, anxiety in the open field test increased after administration of both doses of IA and decreased in the light-dark test and elevated plus maze test after small doses of IA. In the forced swimming test, administration of both doses of IA was followed by an increase in the duration of immobility (a behavioral symptom of depression). Administration of the intermediate (but not the small) dose of IA was followed by increases in the contents of dopamine and its metabolites in the olfactory bulb and decreases in the nucleus accumbens; the noradrenaline content decreased in the prefrontal cortex. It is suggested that these neurochemical changes in the brain may underlie the behavioral symptoms of depression induced by intranasal administration of intermediate doses of IA. Depression-like behavioral symptoms occurring after administration of small doses of IA were evidently not linked with changes in brain monoaminergic systems but could be due to other mechanisms.