Amisulpride-d5 is intended for use as an internal standard for the quantification of amisulpride by GC- or LC-MS. Amisulpride is a dopamine D2 and D3 receptor antagonist (Kis = 3 and 3.5 nM, respectively). It is also an antagonist of the serotonin (5-HT) receptor subtypes 5-HT2B, 5-HT7, and 5-HT7A (Kis = 13, 11.5, and 135.5 nM, respectively). It is selective for these receptors over a panel of 39 additional receptors, ion channels, and transporters (Kis = >1,000 nM for all). Amisulpride increases 7-OH-DPAT-induced decreases in dopamine and acetylcholine release in electrically stimulated rat striatal slices (EC50s = 2.2 and 1.2 nM, respectively). It increases the levels of dopamine and the dopamine metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) in rat striatum and nucleus accumbens when administered intraperitoneally at a dose of 10 mg/kg. Amisulpride decreases immobility time in the forced swim test in rats, as well as reduces stress-induced decreases in sucrose consumption in a rat model of depression induced by chronic mild stress.