Pharmacotherapies utilizing long-acting agonists and mixed function agonists-antagonists have been successful in the treatment of
opiate addiction but no comparable treatment exists for
cocaine abuse. Long-acting tropane analogues have been synthesized that could be candidates for such
pharmacotherapies. 2beta-propanoyl-3beta-(4-tolyl)-tropane (PTT) is one such compound that is a relatively selective
dopamine (DA) transporter blocker that has a significantly longer duration of action than
cocaine. The purpose of this study was to assess the effects of PTT on the intravenous
self-administration of
cocaine,
heroin, or
cocaine/
heroin combinations. Groups of rats were trained to self-administer
cocaine,
heroin, or
cocaine/
heroin combinations using a within session dosing procedure in which three doses were available each session. PTT pretreatment reduced
cocaine and
cocaine/
heroin combinations intake in a dose-dependent manner while having only minor effects on
heroin intake. These results suggest that the neurobiological substrates of
cocaine and
heroin self-administration are different, and that these
cocaine/
heroin combinations may function more like
cocaine alone, even when the dose of
heroin in the mixture will function independently as a reinforcer. These results further support the potential use of long-acting
dopamine reuptake inhibitors as pharmacotherapeutic adjuncts to a comprehensive treatment program for
cocaine and
cocaine/
heroin abuse.