Hindlimb extensor reflex of spinal rats given tranylcypromine stereoisomers

Effects of tranylcypromine enantiomers on monoamine uptake and release and imipramine binding

Studies were carried out in vitro to determine effects of tranylcypromine enantiomers ([+]- and [-]-TCP) on uptake and release of 5-HT, DA and NA in rat synaptosomes and on imipramine binding to rabbit platelets. (+)-TCP was more potent than (-)-TCP as inhibitor of 5-HT uptake and imipramine binding, whereas (-)-TCP was more potent than (+)-TCP as inhibitor of DA and NA uptake. The enantiomers differed only slightly in their effects on monoamine release. The findings agree with previous reports on the stereo-selectivity of monoaminergic mechanisms toward TCP enantiomers, and support the notion that the 5-HT uptake site may be associated with the imipramine binding site.

Stereoselective effect of tranylcypromine enantiomers on brain serotonin

Brain levels of 5-HT, 5-HIAA and L-tryptophan were measured in reserpinized rats given the enantiomers of tranylcypromine (TCP). (+)-TCP (1.5-30 mg/kg) increased levels of 5-HT, whereas (-)-TCP failed to affect 5-HT levels. (+)-TCP at high dosage (30 mg/kg) decreased brain levels of 5-HIAA, whereas (-)-TCP failed to affect 5-HIAA levels. Neither (+)-TCP nor (-)-TCP influenced brain levels of L-tryptophan. The effects of (+)-TCP on behavior resembled those of drugs which influence 5-HT processes, whereas (-)-TCP failed to produce 5-HT-dependent behaviors. The findings support the notion that TCP enantiomers have stereoselective effects on serotonergic mechanisms.