Effects of terguride on rat heroin self administrafion under fixed ratio and progressive ratio schedule

Objective To characterize the effects of terguride, a partial dopamine agonist at the D2 receptor subtype, on intravenous self-administration of heroin in fixed ratio and progressive ratio schedule. Methods The male adult Sprague-Dawley rats were trained to serf administrate heroin under fixed ratio and progressive ratio, water self administration was set as natural reward control group. The effects of acute administration of terguride (0.1-0.4 mg/kg i. p. ) or saline were compared. Results Compared with saline group, terguride significantly and dose-dependently reduced the responding of heroin self administration under fixed ratio. In addition, terguride at the dose of 0.4 mg/kg significantly decreased the maximum number of responses delivered for a single injection of heroin (" breaking point") under progressive ratio. Terguride had no significant effect on water self administration under fixed ratio. Conclusion The D2 partial agonist terguride could reduce the reinforcing property of heroin. Key words: Receptors, dopamine D2;  Dopamine agonists;  Terguride;  Heroin dependence; Self administration