Differences in paired-pulse inhibition and facilitation in the dentate gyrus and XXXX field between dorsal and ventral rat hippocampus.

@entity308 @entity12463 @entity33797 @entity1251 @entity141
UNASSIGNED: We studied the processes of inhibition and facilitation in the dentate gyrus (DG) and the @entity1251 field by examining the effects of paired-pulse stimulation on the evoked @entity12463 ( @entity12463 ) in dorsal (DH) and ventral (VH) hippocampal slices from the adult rat. The antidromic-orthodromic (A-O) and the orthodromic-orthodromic (O-O) paired-pulse stimulation protocols were used at varying inter-pulse intervals (IPI). In the DG, the A-O stimulation produced an early @entity308 of @entity12463 lasting 30-40ms which was significantly stronger in the VH compared with DH. The O-O stimulation produced a biphasic pattern of effects, in both dorsal and ventral DG, consisting of an early @entity308 of @entity12463 followed by facilitation at relatively longer intervals. In the DH but not the VH the phase of facilitation was followed by a late @entity308 of @entity12463 (>200ms). In the @entity1251 field both A-O and O-O stimulation had a biphasic effect consisting of an early phase of strong @entity308 of similar strength in DH and VH. The @entity308 was followed by a phase of facilitation which was more pronounced with O-O stimulation. The facilitation observed with the O-O stimulation was much stronger in DH than VH and in DH only it was significantly reduced by the antagonist of GABAB receptors @entity33797 . Furthermore, the facilitation was insensitive to changes in [ @entity141 ]o in both hippocampal poles. These findings suggest that the dorsal compared with ventral DG is more amenable to fast-frequency input but filters out slow-frequency inputs more reliably while the gating and amplification of the excitatory input in the @entity1251 circuitry is more prominent in DH than in VH.
