Prior extended daily access to cocaine elevates the reward threshold in a conditioned place preference test

摘要: We have previously shown that extended-access subjects exhibit heightened motivation for cocaine in the runway model, as reflected by reduced number of retreats. This could reflect either an increase cocaine-induced reward or a decrease aversion. The current experiment was therefore devised to assess and aversion rats using place conditioning test. Rats trained lever press intravenous (IV) (0.25 mg/infusion) were provided 6-hour daily access drug over 10 days. Lever pressing control produced IV infusions saline. Following self-administration, underwent immediate delayed effects (1.0 2.5 mg/kg, IV). In subjects, low dose conditioned places preferences (CPPs), while aversions (CPAs). contrast, animals receiving 6 hours, exhibited but not preferences; effect reversed when increased. Additionally, group, associated with reduction zif268 immunoreactivity medial prefrontal cortex nucleus accumbens shell zif268-positive cells central amygdala. Collectively, these data suggest extended produces shift subject's perceived threshold is paralleled alterations activity both stress pathways.