Baclofen decreases methamphetamine self-administration in rats

In the present study we tested the hypothesis that baclofen, a GABA-B receptor agonist, attenuates methamphetamine self-administration. Fifteen rats were trained to self-administer i.v. injections of methamphetamine (0, 0.0625, 0.125 and 0.25 mg/kg/ injection) on a progressive ratio schedule of reinforcement, and then were tested under the influence of two doses of baclofen (2.5 or 5.0 mg/kg, i.p.). Baclofen significantly reduced break points at all doses of methamphetamine, producing a dose-orderly shift of the methamphetamine dose-response function to the right. These data suggest that pretreatment with baclofen reduces methamphetamine reward. These data are consistent with other studies showing impairment of drug reward after pretreatment with baclofen and add further support to the idea that GABA-B agonists may be useful in the treatment of drug addiction.