Figure 1. The sequence of experimental events.

Panel a illustrates the timeline of experimental events for the in vivo microdialysis study. Rats were implanted with a unilateral cannula into the dorsal striatum and a catheter into the jugular vein. Following recovery, the rats were habituated to the in vivo microdialysis apparatus and to the i.v. infusion procedure on 2 daily sessions. On the following test day, microdialysis probes were inserted into the dorsal striatum and i.v. catheters were tethered to the cocaine infusion set up. Each rat received an i.v. infusion of 2 mg/kg cocaine, delivered over 5, 45 or 90 s, in counterbalanced order, with infusions administered 90 minutes apart. Dialysate samples were collected every minute for 5–10 minutes before each infusion and for 15 minutes thereafter. Panel b shows the sequence of experimental events for the psychomotor activity study. Rats were implanted with an intrajugular catheter and allowed to recover for 7 days. Rats were then habituated to the psychomotor activity cages and i.v. infusion lines on 2 daily sessions. On the following test day, rats were tethered to the cocaine infusion lines and locomotor activity was measured. Each rat received i.v. cocaine (2.0 mg/kg/infusion) delivered over 5, 45 and 90 s, in counterbalanced order, with infusions administered 90 minutes apart.