Figure 4.

Mean ± SEM percent time spent in the designated compartment. Following acquisition trials to MA (days 7–10) the animals demonstrated a shift from the preferred (day 6) to the nonpreferred (day 11) compartment. During extinction trials (days 12–16) the animals received icv infusions of divalinal 5-min prior to access to both compartments for 30 min on each day and evidenced a shift back to the preferred compartment. On days 17–20 the rats were rested in their home cages. On days 21 and 22 each rat received MA followed 5-min later with access to both compartments. During these two days there was a clear shift back in favor of the nonpreferred compartment indicating reinstatement of dependence. * p < 0.01.