Double dissociation of hippocampal and dorsal-striatal memory systems by posttraining intracerebral injections of 2-amino-5-phosphonopentanoic acid

Rats received an 8-trial training session on a spatial or cued task in a water maze, followed by a posttraining intracerebral injection of AP5 or saline. On a retention test 24 hr later, latency to mount the escape platform was used as a measure of memory. Intrahippocampal (10 mu g), but not intra-dorsal striatal (2, 5, or 10 mu g), injection of AP5 impaired memory in the spatial task. In contrast, intra-dorsal striatal (2 mu g), but not intrahippocampal (2, 5, or 10 mu g) injection of AP5 impaired memory in the cued task. Intracerebral injections of AP5 delayed 2 hr posttraining were ineffective. The findings indicate a double dissociation of the roles of the hippocampus and dorsal striatum in memory, a role for N-methyl-D-aspartate receptor function in posttraining memory processes, and a glutamatergic modulation of both hippocampal and dorsal striatal memory processes, suggesting that different forms of memory may share a similar neurochemical basis.