Notes: Citalopram is a selective serotonin (5-HT) reuptake inhibitor (SSRI) with an IC50 value of 1.8 nM for 5-HT reuptake in rat brain synaptosomes.{38122} It is selective for 5-HT reuptake over that of dopamine and norepinephrine (IC50s = >6 mM). Citalopram potentiates headweaving and tremor induced by 5-hydroxy-L-tryptophan (Item No. 20539) in mice (ED50s = 0.61 and 0.66 mmol/kg, respectively). It also acts as an antagonist of nicotinic acetylcholine receptors (IC50 = 0.93 µM).{23021} Formulations containing citalopram have been used to treat depression. This product is also available as an analytical reference standard (Item No. 23252).