rac-Rotigotine Hydrochloride is a high potency and selectivity agonist for D-2 receptor with Ki of 0.69 nM. IC50 Value: 0.69 nM(Ki)Target: D-2 receptorin vitro: rac-Rotigotine showed high potency (Ki = 0.69 nM) and selectivity for D-2 receptors as compared to its potency and selectivity at various other neuronal receptors (Ki in nM): D-1 (678) dopamine, alpha 1-(534) and alpha 2-(195) adrenoceptor, S1-(6940) and S2-(5900) serotonin and muscarine (2660). Very low activity (Ki greater than 10(-5) M) was seen at the beta-adrenoceptor, A1-adenosine, GABAA and benzodiazepine receptors. Furthermore, rac-Rotigotine inhibited the calcium-dependent release of [3H]dopamine (IC50: 4 nM) and [3H]acetylcholine (IC50: 6.3 nM) from rabbit striatal slices in the nanomolar range. These effects of rac-Rotigotine were mediated through activation of D-2 dopamine autoreceptors and D-2 dopamine heteroreceptors, respectively.in vivo: Presynaptic dopaminergic activity in vivo was measurable as an inhibition of the locomotor activity of mice, and in this model rac-Rotigotine was more effective than apomorphine. Moreover, the effect of rac-Rotigotine could be antagonized by sulpiride but not by yohimbine. rac-Rotigotine was equipotent with apomorphine in inducing circling behaviour in 6-OHDA-lesioned rats. rac-Rotigotine had almost no serotonergic activity in vivo.

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