Figure 2.

Self-administration of conventional benzodiazepine agonists under a progressive-ratio schedule of i.v. midazolam or cocaine injection. (a) Intravenous self-administration of midazolam by rhesus monkeys trained to press a lever to obtain injections of 0.03 mg/kg/injection of midazolam (N=4; filled symbols, ‘midazolam baseline') or 0.03 mg/kg/injection of cocaine (N=4; open symbols, ‘cocaine baseline'). Data are mean (± SEM) injections per session, out of a total of 20 injections available in a daily session. Points above ‘V': vehicle tests. Note that *P<0.05 vs vehicle (Bonferroni t-tests). (b) Self-administration of lorazepam under the same conditions as described for panel a.