Abstracts

Rationale: Field potential oscillations reflect rhythmic synchronized synaptic potentials and/or firing by populations of neurons. These oscillations are characteristic of and perhaps causally involved in a variety of physiological and pathophysiological states such as cognition, sleep, and seizures. We sought to provide a spatio-temporal analysis of very fast oscillations associated with triggered epileptiform events in Ammon’s horn. Methods: Rat ventral hippocampal brain slices were cut and maintained in a recording chamber with 64 simultaneous extracellular recordings. Brief single stimulus pulses were applied with bipolar electrodes to the CA3 or CA1 regions of hippocampus. After exporting the recordings into Matlab, we performed a frequency analysis of the oscillatory periods. Results: We found that single pulses in the presence of GABA_A receptor blockers in the ACSF triggered epileptiform events that contained episodes of very fast oscillations lasting 50-150 msec. These epileptiform events had a mean frequency of 176 ± 74 Hz, with the oscillations of largest valley-to-peak amplitude located in the CA3c region. Conclusions: These findings suggest an important role of CA3c in epileptiform activity, perhaps due to differences in the excitatory interconnectivity of area CA3c.