Role of dorsal CA3 recurrent collaterals in cue-induced pattern completion leading to relapse into drug taking and drug seeking behaviors

In the contest of drug addiction, relapse is defined as the return to drug seeking and drug taking behavior after a prolonged period of abstinence. Relapse is a serious problem that still requires extensive research in order to generate sufficient knowledge of the mechanisms that mediate it. Often, the role of craving is cited as a primary motivating factor for relapse. One possible mechanism that could support this observation is known as pattern completion, a process wherein presentation of an incomplete stimulus complex reinstates the complete, previously learned pattern. It has been proposed that during retrieval of information, the dorsal CA3 recurrent collaterals of the hippocampus play a major role in retrieving complete previously learned patterns in the face of an incomplete stimulus complex input to the hippocampus (pattern complietion). Support for the operation of a pattern completion process is based on a spatial pattern completion task in which-the effects of naloxone injections into the dorsal CA3 sub-region of the hippocampus revealed impairment of pattern completion in the presence of varying numbers of available cues. We used a variant of the conditioned place-preference task in which the number of available cues was parametrically adjusted to assess the role of pattern completion in cue-induced reinstatement of drug-seeking behavior and to determine whether disruption of pattern completion secondary to infusion of naloxone into the dorsal CA3 region disrupts cue-induced reinstaement. Results indicate that naloxone will disrupt the reinsta tement (preference for cocaine conditioned cues over saline conditioned cues) for one cue, but not for all four cues, suggesting a significant impact on pattern completion within the dorsal CA3 region.