“Daily injections of dihydroxyphenylalanine (DOPA), a precursor for dopamine synthesis, given 12 hr after daily injections of 5-hydroxytryptophan (5-HTP), a serotonin precursor, induced uterine growth and increased serum thyroxine and luteinizing hormone (LH) concentrations in scotosensitive female hamsters maintained on short daylengths.”