Effects of tranylcypromine stereoisomers, clorgyline and deprenyl on open field activity during long term lithium administration in rats.

Locomotor activity of male rats was studied in an open field after an i.p. injection (15 mg/kg) of the d- or l-isomers of tranylcypromine (d-Tc and l-Tc, respectively) or after s.c. injection of either clorgyline (0.5, 1 or 5 mg/kg) which selectively inhibits Type A MAO or deprenyl (0.5, 5 or 10 mg/kg) which selectively inhibits Type B MAO. The rats were fed a diet containing either no lithium (control group) or lithium chloride (lithium group) for at least 28 days prior to tests. In the control group, d-Tc increased ambulation while l-Tc, deprenyl and clorgyline failed to affect activity. In the lithium group, d-Tc and deprenyl increased ambulation, l-Tc increased ambulation and rearing, while clorgyline failed to affect activity. Lithium appeared to potentiate the behavioral effects of deprenyl and l-Tc. Symptoms of serotonin-dependent hyperactivity appeared in the control group and lithium group given d-Tc. The role of biogenic amines in the effects of the drugs on open field activity is discussed.