Suppression of XXXX -induced @entity410 activity: evidence for a permanent role for the hippocampus in contextual memory.

@entity5186 @entity410 @entity1024 @entity1022 @entity4524 @entity1372 @entity2730 @entity143 @entity35 @entity2359
Damage to the hippocampus (HPC) using the excitotoxin @entity1024 ( @entity143 ) can cause @entity5186 for contextual fear memory. This @entity2730 is typically attributed to loss of cells in the HPC. However, @entity143 is also known to cause intense neuronal discharge ( @entity410 activity) during the hours that follow its injection. These @entity410 may have detrimental effects on retrieval of memories. Here we evaluate the possibility that @entity5186 is due to @entity143 -induced @entity410 activity or cell damage per se. To assess the effects of @entity143 induced activity on contextual memory, we developed a lesion technique that utilizes the @entity2359 effects of @entity143 while at the same time suppressing possible associated @entity410 activity. @entity143 and @entity1022 ( @entity4524 ), a @entity1372 channel blocker, are simultaneously infused into the @entity35 HPC, resulting in extensive bilateral damage to the HPC. @entity4524 , co-infused with @entity143 , suppresses propagation of @entity410 activity. @entity35 received pairings of a novel context with foot shock, after which they received @entity143 -induced, @entity4524 + @entity143 -induced, or no damage to the HPC at a recent (24 hours) or remote (5 weeks) time point. After recovery, the @entity35 were placed into the shock context and freezing was scored as an index of fear memory. @entity35 with an intact HPC exhibited robust memory for the aversive context at both time points, whereas @entity35 that received @entity143 or @entity143 + @entity4524 lesions showed a significant reduction in learned fear of equal magnitude at both the recent and remote time points. Therefore, it is unlikely that observed @entity5186 in contextual fear conditioning are due to disruption of non-HPC networks by propagated @entity410 activity. Moreover, the memory deficit observed at both time points offers additional evidence supporting the proposition that the HPC has a continuing role in maintaining contextual memories.
