Differential modulation of the discriminative stimulus effects of methamphetamine and cocaine by alprazolam and oxazepam in male and female rats

Drug users often combine benzodiazepines with psychostimulants, such as methamphetamine. However, very little research has been conducted on this type of polydrug use, particularly in female subjects. The present study was therefore designed to examine the effects of two benzodiazepines, alprazolam and oxazepam, on the discriminative stimulus effects of methamphetamine and cocaine in both male and female rats. Rats were trained to discriminate methamphetamine (1.0 mg/kg, ip) or cocaine (10 mg/kg, ip) from saline using a two-lever operant, food-reinforced, drug discrimination design. Pretreatment with oxazepam (5, 10 and 20 mg/kg, ip) significantly attenuated methamphetamine discrimination in both male and female rats. In contrast, however, the high dose of alprazolam (4 mg/kg, ip) actually augmented the subjective effects of lower doses of methamphetamine (0.125 and 0.25 mg/kg, ip). Oxazepam produced similar effects on the subjective effects of cocaine as with methamphetamine, significantly reducing cocaine discrimination in both male and female rats. However, neither the high nor low dose of alprazolam (2 and 4 mg/kg, ip) produced any apparent effect on cocaine discrimination. Finally, while similar results were observed in both male and female rats across these experiments, methamphetamine and cocaine discrimination were more sensitive to oxazepam in female subjects. The results of these experiments suggest that alprazolam and oxazepam can differentially affect the subjective effects of methamphetamine and cocaine. These results also demonstrate that alprazolam can differentially affect the discriminative stimulus effects of methamphetamine and cocaine.