Competitive inhibition of sodium-dependent high affinity choline uptake by harmala alkaloids

The actions of five harmala alkaloids on the sodium dependent high affinity choline uptake activity in rat striatal synaptosomes was investigated. All five compounds were found to be competitive inhibitors of the uptake system. Harmalol (Ki approximately 3.4 microM) and 2-methylharmine (Ki approximately 5.7 microM) were found to be relatively potent inhibitors in a series with an ascending order of inhibitory potency of harmaline less than 2-methylharmaline less than harmine less than 2-methylharmine less than harmalol.