The lumped constant of α-methyl-l-tryptophan is not influenced by drugs acting through serotonergic system

► Lumped constant converts brain trapping of tracer α-[14C]MTrp into 5-HT synthesis. ► The effects of drugs on the lumped constant (LC) stability were investigated. ► The regional values of LC in each of these three sets were normally distributed. ► LC values calculated as the mean did not differ significantly between experiments.