Rats were anesthetized with urethane (1.5 g/kg i.p.) and immobilized in a stereotaxic apparatus (David Kopf Instruments, Tujunga, CA, USA)(Howard et al. 2011 (link); Howard et al. 2013b (link)). Core temperature was maintained with Deltaphase Isothermal Pads (Braintree Scientific, Braintree, MA, USA). Holes were drilled through the skull in order to position recording, stimulating, and reference electrodes using coordinates from a rat brain atlas (Paxinos and Watson 1986 ). Bregma and dura were used as reference points, and all coordinates are in mm. Initially, the stimulating electrode was positioned just dorsal to the medial forebrain bundle (AP -4.6, ML +1.4, DV -7.0), carbon-fiber microelectrodes were lowered ipsilaterally into the DM and DL striatum (AP +0.4, ML +1.8 and +3.8, respectively, DV -4.5), and the reference electrode was placed in the contralateral superficial cortex. The stimulating electrode and carbon-fiber microelectrodes were then incrementally lowered to record robust levels of electrically evoked DA. After optimization, the position of these electrodes was not changed throughout the duration of the experiment.