In addition to the place preference test, we examined the development of locomotor sensitization to repeated doses of cocaine in control and antibiotic-treated animals. Prior to the start of cocaine testing, animals from both groups received three days of injections with saline only to monitor baseline locomotor activity, and to allow animals to habituate both to the locomotor chambers and to the injections. Analysis of these baseline days demonstrated the expected mean effect of time (F(2,16) = 22.95; p < 0.001), but, importantly, there were no treatment (F(1,8) = 1.16; p = 0.31) or time x treatment interactions (F(2,16) = 1.16; p = 0.34) (Fig. 3d - left). This makes the important point that antibiotic treatment on its own does not affect locomotor behavior. When we looked at locomotor activity after cocaine treatment, we obtained results with a similar pattern to those seen with CPP. At 10 mg/kg dosing there was a robust sensitization response across the five-day period for both groups using repeated-measures two-way ANOVA (Main effect of time: F(4,32) = 29.53; p < 0.0001). However, there was no
