Effect of monoamine precursors on the forced-swimming test in mice.

The antidepressant properties of monoamine precursors were evaluated by the forced-swimming test for mice developed by Porsolt et al. DOPA but not 5-hydroxytryptophan (5HTP) shortened immobility at doses that did not increase locomotor activity. Although L-threo-dihydroxyphenylserine (DOPS), an artificial norepinephrine (NE) precursor, did not change immobility in intact mice, DOPS significantly reduced immobility in mice pretreated with the selective NE neurotoxin DSP4. These results suggest possible antidepressant properties of DOPA and DOPS, the latter of which may act as an antidepressant in a certain NE-depleting condition.