Talipexole (B-HT920) is a dopamine agonist that has been proposed as an antiparkinsonian agent.Target: Dopamine ReceptorB-HT920 is a selective alpha 2-adrenoceptor agonist. The effects of B-HT920 have been specified using the alpha-adrenergic antagonists yohimbine and prazosin and the dopamine antagonist haloperidol. Yohimbine could not antagonize any of the actions of B-HT920. Pretreatment with prazosin showed a decrease in the loss of body weight caused by B-HT920, while pretreatment with yohimbine showed that B-HT920 induced an increased loss in body weight. These data suggest that B-HT920 under certain conditions exerts dopamine-agonistic actions in stimulating locomotor activity and alpha 1-adrenergic actions in inducing salivation and enhanced loss of body weight [1]. Concomitant treatment with talipexole, an anti-parkinsonian drug, inhibited MPTP-induced autolysis and individual death in a concentration-dependent manner. Pramipexole showed a similar protective effect. In addition, post-treatment with talipexole at 1 hr after MPTP completely inhibited MPTP-induced individual death. Although MPTP treatment caused 30% of the planarians to undergo autolysis and individual death within 12 hr, post-treatment with talipexole even at 12 hr completely rescued the remaining 70% of the planarians from death. These results suggest that the MPTP-treated planarian may be useful as a novel parkinsonian model in which talipexole has a protective effect even in the case of post-treatment [2].

[1]. Van der Laan, J.W., Dopaminergic and alpha 1-adrenergic properties of B-HT920 revealed in morphine-dependent rats. Pharmacol Biochem Behav, 1987. 26(2): p. 265-9. [2]. Kitamura, Y., J. Kakimura, and T. Taniguchi, Protective effect of talipexole on MPTP-treated planarian, a unique parkinsonian worm model. Jpn J Pharmacol, 1998. 78(1): p. 23-9.