Eticlopride, a Potent Substituted Benzamide Compound Useful for the Labelling of Rat Central Dopamine-D₂ Receptors in vitro and in vivo

Abstract

The new substituted benzamide compound eticlopride ((S)-(-)-5-chloro-3-ethyl-N-[(1-ethyl-2-pyrrolidinyl)methyl]-6-methoxysalicylamide hydrochloride; FLB 131) has been shown to selectively block the dopamine-D² receptors in the rat brain. Eticlopride was thus found to inhibit the apomorphine induced syndrome at very low doses (ED⁵⁰ for inhibition of stereotypies: 200 nmol/kg i.p. and for hyperactivity: 23 nmol/kg i.p.). Similar to other substituted benzamides eticlopride induces a weak form of catalepsy only at high doses (ED⁵⁰ 2.5 umol/kg i.p.). In vitro, the compound was found to inhibit dopamine-D² receptors very potently (Table 1). For the further characterization of the receptor binding properties eticlopride was radiolabelled using catalytic hydrogenation to high specific radioactivity and was used for in vitro and in vivo receptor binding studies.