The effect of tryptophan depletion on the action of haloperidol in MK-801-treated rats.

We investigated the effect of tryptophan depletion (tryptophan-free mixture) on locomotor activity in an animal model of schizophrenia, induced by acute administration of 5R,10S-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]-cyclohepten-5,10-imine hydrogen maleate (MK-801), and the influence of the tryptophan-free mixture on the action of the typical antipsychotic haloperidol. Male rats were pre-treated with haloperidol 60 min after receiving the tryptophan-free mixture (or water). We measured total distance travelled in an open field during a 90-min period.