Intravenous self-administration of dopamine receptor agonists by rhesus monkeys

Pharmacological studies have provided important information relevant to the behavioral role of central nervous system (CNS) dopamine (DA) as well as the existence of multiple DA receptors in the CNS. In the present experiment, the i.v. self-administration of several compounds that are direct DA receptor agonists was evaluated in rhesus monkeys. Apomorphine, piribedil, propylbutyldopamine and bromocriptine were self-administered by at least half of the animals tested, whereas SKF 38393 failed to maintain self-administration. Each of the compounds that was self-administered is an agonist at the DA2 receptor that has been demonstrated in the periphery, whereas SKF 38393 is principally a DA1 agonist. The results suggest that a DA receptor that is similar to the DA2 receptor is involved in this behavioral effect. In addition, the results are consistent with the hypothesis that CNS DA is involved in the reinforcing properties of psychomotor stimulants.