Acute interferon-alpha administration modulates sucrose consumption in the rat.

One of the two core symptoms of depression as defined by the Diagnostic and statistical manual of mental disorders (DSM-IV) (American Psychiatric Association) is anhedonia, or a loss of interest or pleasure. Sucrose consumption has been described as a valid measure of sensitivity to reward. In the present set of studies, changes in sucrose consumption (three-bottle test using 1, 8 and 32% sucrose) were taken as a measure of the anhedonic effect of interferon-alpha (IFN-alpha). Sucrose tests were carried out following the i.p. administration (20 min pre-treatment time) of Recombinant Human Interferon-alphaA (rHIFN-alpha), 10(1), 10(2), 10(4) units(U) and Rat Interferon alpha (rRIFN-alpha), 1,10 and 100 IRU. Both types of IFN-alpha produced a decrease in sucrose consumption and drinking rate (DR) at the highest doses, with the greatest inhibition being at the lowest sucrose concentration (1%). Longer pre-treatment times with rHIFN-alpha (40 and 80 min prior to commencement of 1 h drinking test) resulted in insignificant effects. Significant hypothermia relative to vehicle-injected rats was observed following interferon administration in the 20 min pre-treatment condition, but showed no significant difference when compared to vehicle at 40 or 80 min. Overall these results confirm a depression-like behavioural syndrome (anhedonia) following administration of IFN-alpha.