Depressive-like huddling behavior during IFN-alpha or saline administration. IFN-alpha (20 MIU/m²) or saline was administered s.c. for 4 weeks to 8 rhesus monkeys in counterbalanced fashion, and behavior was assessed weekly by videotape at 2 hours post-injection. Administration of IFN-alpha was associated with persistent huddling behavior in 3 animals (A). A photograph of a monkey huddling during IFN-alpha administration appears in B. Data are presented as the mean (+/- SEM) for these 3 animals at each time point during either saline or IFN-alpha treatment. * - indicates a significant difference between treatment groups at indicated time points as revealed by post-hoc analyses (p<0.05). † - indicates the initiation of saline or IFN-alpha administration (day 1).