Figure 5.

Expressing human immunodeficiency virus 1 (HIV-1) Tat protein reinstates extinguished cocaine-conditioned place preference (CPP). (a) Time course schematic of extinction and reinstatement experiment. In week 1, C57BL/6J or uninduced GT-tg bigenic mice were preference tested (triangles) the days preceding and following place-conditioning with cocaine (10 mg/kg, s.c.) and saline daily for 4 days (squares). Mice were tested for place preference twice weekly during weeks 2, 3, and 4 (circles). After extinction (3 weeks after conditioning; 5 weeks into the experiment) mice were induced to express Tat protein (doxycycline 100 mg/kg, i.p., for 7 days) and tested again for place preference (right-most triangle). (b) Results of extinction and reinstatement experiment. C57BL/6J (white bars) and GT-tg bigenic (gray bars) mice demonstrated significant cocaine-CPP compared with pre-conditioning preferences. Three weeks after the completion of conditioning, mice demonstrate extinction of CPP. Following induction of HIV-1 Tat protein, GT-tg bigenic, but not C57BL/6J controls, demonstrate a significant reinstatement of cocaine-CPP. *Indicates significant difference from respective pre-CPP response, p<0.05, repeated measures analysis of variance (ANOVA).