Supplementary Figure 2: Injections of DHPG or Ro67-7476 into the NAc core have no effect on sucrose self-administration

To control for nonspecific effects of DHPG and Ro67-7476 on motivated behavior, the effects of intra-NAc core injections of these compounds on sucrose self-administration were assessed. (a) As shown in the experimental timeline, drug-naïve rats underwent intracranial surgery to implant guide cannulae in the NAc core and, following 7 days of recovery, began daily sucrose self-administration sessions. During these 2 h sessions, a nose-poke in the active hole resulted in a sucrose pellet being dispensed in the food hopper (fixed ratio 1) and was paired with a cue-light inside the hole and a time-out period (10 sec), while responses in the inactive hole were without consequence. After 5 days of training, rats received intra-NAc core injections of vehicle, DHPG (0.25nmol/0.5μl/side), or Ro67-7476 (0.005nmol/0.5μl/side) 10 min prior to the start of the sucrose self-administration session. (b) No group differences in number of pellets dispensed were observed on the test day (F_2,16=0.052, p=0.95), and the average number of pellets dispensed on the test day in each group did not differ from the average number of pellets dispensed during the 5 days of training. These data show that intra-NAc core injections of DHPG and Ro67-7476 do not affect motivation to obtain a natural reward and suggest that their effects on cue-induced cocaine seeking are due to a reduction in cocaine craving rather than non-specific alterations in motivated behavior. Rats were also tested for an additional two days following the test injection day to ensure that the injections received on day 6 had no residual effect on sucrose self-administration behavior. No group differences in number of pellets dispensed were observed on either day 7 or 8 (data not shown). Data are shown as average number of pellets dispensed (± s.e.m.) during the 2 h session. Control, n=6 rats; DHPG, n=7 rats; Ro67-7476, n=7 rats. (c) Location of cannnulae placements in NAc core for all rats included in this study. Numbers represent distance anterior to bregma (mm).