Extracellular and intracellular recordings were made from slices taken from the dorsal (DH) and ventral (VH) part of rat hippocampus. Using paired-pulse stimulation of Schaffer collaterals, at different interpulse intervals (IPIs), and records of the population spike (PS) we found that the strength and duration of paired-pulse inhibition was much weaker in VH compared to DH slices: at the IPI of 10 ms the decrease of PS in VH (40%) was significantly smaller compared to that in DH slices (76%), while at 20 ms the decrease of PS in DH slices (60%) corresponded to facilitation in VH slices. Moreover, the amplitude and duration of intracellularly recorded fast inhibitory postsynaptic potentials (fast-IPSPs) were found significantly smaller in VH (5.2+/-0.6 mV, 54.8+/-5.8 ms) than in DH (11.2+/-1.1 mV, 105+/-10 ms) neurons. The smaller and shorter fast-IPSP recorded in VH neurons may at least in part explain the results in paired-pulse inhibition. The demonstrated weaker inhibition may underlie the higher propensity of the ventral hippocampus for epileptiform activity.
Copyright 2002 Elsevier Science B.V.