Here we show in DAT GLS1 conditional heterozygous (cHET) mice — with a DAT (Slc6a3)-driven Gls1 reduction — that DA neuron GLU cotransmission is reduced in a frequency dependent manner, without affecting DA neuron development or DA release, and that behaviors that rely on the motivational salience-encoding function of DA neurons are selectively affected, with implications of DA neuron GLU cotransmission for schizophrenia pharmacotherapy. Here, SLC6A3 is linked to schizophrenia.