Comparing the Seizure-induced Impairment of Short-term Plasticity in Dorsal and Ventral Hippocampus in Kindled Mice.

Introduction: The differences among dorsal and ventral hippocampal neural circuits affect synaptic plasticity. In this study, we aim to compare the occurrence of short-term plasticity in the field excitatory postsynaptic potential (fEPSP) in dorsal and ventral hippocampal CA1 areas following kindled seizures.

Methods: Animals (male C57 B6/J mice, 12 weeks of age) were kindled by intraperitoneal injections of pentylenetetrazole (PTZ), and fEPSPs were recorded from dorsal and ventral hippocampal slices. Short-term plasticity was evaluated by measuring fEPSP-slope and fEPSP-area following paired-pulse stimulation delivered at three inter-pulse intervals (20, 80, and 160 ms).

Results: In control slices, the fEPSP-slope was greater in the ventral hippocampus compared to the dorsal hippocampus, but there was no difference in the fEPSP-area between the two regions. In hippocampal slices, the fEPSP-slope was similar in the dorsal and ventral regions, but the fEPSP-area was greater in the ventral region compared to the dorsal region. In addition, the fEPSP-area was greater in the kindled group than in the control group only in the ventral hippocampus. PTZ-induced kindled slices showed impaired short-term facilitation, and the paired-pulse index decreased only in the dorsal hippocampus. Kindling had no significant effect on the paired-pulse ratio in the ventral hippocampus.

Conclusion: The seizure occurrence affects the neural activity of the hippocampus in a region-dependent manner. Although kindling increases the fEPSP area in the ventral hippocampus of mice, kindling-induced changes in short-term synaptic plasticity are significant only in the dorsal hippocampus. The difference in the responses of dorsal and ventral poles should be considered in future studies.