When long-term memories are retrieved, they are transiently labile and susceptible to modification by environmental stimuli through a process called reconsolidation.53 The memory of an environmental cue associated with an addictive drug is subject to reconsolidation that is dependent on ERK activity. In rats trained to develop cocaine CPP, an injection of U0126 into the NAc core immediately after CPP testing prevents subsequent expression of CPP on retesting.52 The specific retrieval of the long-term memory is crucial for MEK inhibition to affect this memory. Rats treated with U0126 without a prior CPP test that would retrieve the long-term association did not show a deficit in CPP expression in subsequent tests.52 MEK inhibition also affects CPP memory reconsolidation for other addictive drugs. PD98059 injections into the VTA inhibit reconsolidation of methamphetamine CPP.31 Systemic SL327 injections inhibit reconsolidation of morphine CPP44 in rodents. ERK activation ultimately results in increased protein synthesis. Inhibition of protein synthesis using systemic anisomycin during long-term memory retrieval also impairs reconsolidation of cocaine44 and morphine CPP.54 In addition to CPP reconsolidation, ERK activation is crucial for the reconsolidation
