Aim: To compare the pharmacological characteristics of 12-chloroscoulerine (CSL) enantiomers to dopamine (DA) receptors.
Methods: Radioligand receptor binding assay with calf striatum and behavioral tests of mice or rats were used.
Results: In the competitive binding assay, the affinities (Ki) of l-CSL to D1 and D2 receptors were 5.7 nmol.L-1, while those of d-CSL for D1 and D2 receptors were 135 and 9150 nmol.L-1, respectively. The Ki of dl-CSL to D1 and D2 receptors were 8.9 and 9.6 nmol.L-1, respectively, which were slightly weaker than that of l-CSL. In the behavioral experiments, CSL enantiomers 5-60 mg.kg-1 antagonized the stereotypy induced by apomorphine in rats, and 5-150 mg.kg-1 produced catalepsy. The enantiomers 10-60 mg.kg-1 reduced the mice jumping behavior induced by amphetamine + levodopa. l-CSL 10-80 mg.kg-1 antagonized the spontaneous locomotor activity of normal or amphetamine-treated mice.
Conclusion: CSL enantiomers are antagonists to DA receptors: l-CSL > dl-CSL >> d-CSL.