L-741626 (3-(4-(4-Chlorophenyl-4-hydroxypiperidino)methyl)indole) is a selective antagonist of D2 dopamine receptor (Ki: 2.4, 100, and 220 nM for human D2, D3 and D4 receptors respectively).

D2 receptor (human):(ki)2.4 nM, D3 receptor (human):100 nM(ki), D4 receptor (human):220 nM(ki)

L-741626 is an effective antagonist (EC50 (D2)=4.46 nM) with some D2 selectivity (EC50 (D3)=90.4 nM), in the functional assay. L-741626 is prepared by literature methods (Ki (D2)=11.2 nM). L-741626 also shows a D3/D2 and D4/D2 selectivity ratio of 15-fold and 136-fold, respectively. Intrinsic activities using inhibition of quinpirole stimulation of mitogenesis in human dopamine D2 or D3 receptors transfected into Chinese hamster ovary (CHO) cells, in a functional assay [2].

In pramipexole-trained male Sprague Dawley rats, L-741626 (1.0 mg/kg; i.h.) is effective at shifting to the right the pramipexole dose-response curve [3]. Coadministration Cocaine with the D2 antagonist L-741626 (3 mg/kg; i.p.; 15 min before Cocaine) for 5 days decreases the Cocaine-induced enhance in microglial TNF-α production in adult mice [4].