The technique for combined electrophysiological and electrochemical recordings has been described previously (Cheer et al., 2005). The apparatus was identical to that described above except that a solid-state relay in the headstage alternated between a current amplifier for voltammetric scans and a voltage follower for unit recording. Units were recorded for 180 ms between voltammetric scans that were collected at 5 Hz. Each scan occupied 20 ms (8.5 ms for the scan and the remainder to allow the amplifiers to settle). Both signals were referenced to the Ag/AgCl electrode. In these experiments, recordings were made at sites where single-units were isolated. Electrical stimulations were made to determine whether dopamine release could be evoked. Following collection of data at one site, the electrode was lowered ~300 μm until another unit was found. This approach often resulted in two sessions per day separated by 5–10 minutes and in some instances partial sessions were recorded (i.e., ~ 9–15 trial/sessions versus full sessions of ~ 20–25 trials/session).
