Ch. 1. The Modulation of Dopaminergic Neurotransmission by Norepinephrine / Charles R. Ashby, Jr. and Jean-Pol Tassin -- Ch. 2. Dopamine-Opioid Interactions in the Basal Forebrain / Lynn Churchill and Peter W. Kalivas -- Ch. 3. Serotonergic Modulation of Midbrain Dopamine Systems / Mark D. Kelland and Louis A. Chiodo -- Ch. 4. Electrophysiological and Biochemical Interactions Between Dopamine and Cholecystokinin in the Brain / Arthur S. Freeman -- Ch. 5. The Modulation of Midbrain Dopaminergic Systems by GABA / Judith R. Walters and Michele L. Pucak -- Ch. 6. A Strategy for Measuring Neurotransmitter Interactions in vivo with Positron Emission Tomography (PET): Neuropsychiatry Implications / Gwen S. Smith, Stephen L. Dewey and Jonathan D. Brodie