To establish the neurotransmitter role(s) of L-3,4-dihydroxyphenylalanine (DOPA) in its own right, we attempted to clarify whether i.p. injection of a DOPA antagonist, DOPA cyclohexyl ester (CHE), would antagonize the behavioral responses of conscious rats to DOPA in the presence of 3-hydroxybenzylhydrazine (NSD-1015) (100 mg/kg i.p.), a central aromatic L-amino acid decarboxylase (AADC) inhibitor.