FIGURE 1.

Pharmacological stimulation of the LPO promotes cocaine seeking, but does not change cocaine self-administration. (A) Timeline of behavioral procedures. SA, self-administration; FR: fixed ratio (number of responses required to obtain one cocaine infusion, depicted with pink line). (B) Location of LPO injections for aCSF (gray) and bicuculline (Bic, purple). (C) Cocaine self-administration behavior. There was slightly more responding in the active hole in rats that would later receive bicuculline compared with those that would later receive aCSF; however, during the last 3 days of self-administration that preceded the self-administration test, groups did not differ. (D) Self-administration test (SA test). Stimulating the LPO with bicuculline did not change active hole or inactive hole responding relative to aCSF or the average of the last 3 days of self-administration (SA Pre). (E) Extinction behavior. Both groups extinguished responding on the previously active hole. There was no difference between groups across extinction nor over the last 3 days of extinction (Ext Pre). (F) Extinction test (Ext Test). Stimulating the LPO with bicuculline reinstated cocaine seeking behavior, observed as increased responding on the previously active hole (HSD, ^∗∗P < 0.01) but not inactive hole (HSD, P = 0.47). Symbols are means ± SEM for each group; lines are individual subjects. See main text for detailed statistics.