Morphology of CA3 neurons in hippocampal slices with nonepileptic and epileptic activity: a light and electron...

In guinea pig hippocampal slices, relations between morphology and spontaneous bioelectric activity of neurons were studied in control saline and with exposure to the epileptogenic drug pentylenetetrazole (PTZ) for 2-3 h. Light and electron microscopic structures of the CA3 region were analysed after recording the membrane potential. Neurons in slices kept in control saline exhibited spontaneous aperiodic bioelectric activities partly mixed with rhythmically occurring burst discharges. In slices exposed to PTZ, these periodic burst discharges and/or paroxysmal depolarization shifts (PDS) predominated. Light microscopic comparison focussing on tissue preservation showed no significant differences between control and PTZ-treated slices. Ultrastructural morphology revealed, on the one hand, no differences regarding spine and synaptic densities, and on the other hand, significantly more irregular electron translucent vacuoles within dendrites of PTZ-treated slices being either randomly distributed or clustered. The vacuoles are interpreted as early changes during epileptic activity.