Tat exposure for 8 weeks and escalated morphine (10 – 40 mg/kg, s.c., b.i.d.) administration for 2 weeks did not significantly affect the latency to interact (A) or percentage of time spent interacting (B) with the unfamiliar mouse, or distance traveled (C) in the social interaction test performed in a novel environment. Similarly, in the social novelty test Tat and morphine did not affect the latency to interact (D) or percentage of time spent interacting with the novel unfamiliar mouse (E), or distance traveled (F). Data are presented as mean ± SEM; n = 9-10 mice per group.