REPEATED ADMINISTRATION OF PENTYLENETETRAZOL ALTERS SUSCEPTIBILITY OFRAT HIPPOCAMPUS TO PRIMED-BURST STIMULATION - EVIDENCE FROM IN-VITRO STUDY ON CA1 OF HIPPOCAMPAL SLICES

The effectiveness of theta pattern primed-bursts (PBs) on development of primed-burst (PB) potentiation was investigated in hippocampal CA1 of pentylenetetrazol-kindled rats. Experiments were carried out in the hippocampal slices from control and kindled rats at two post-kindling periods, i.e. 48-144 h (early phase) and 30-33 days (long-lasting pha se). Field potentials (population excitatory post-synaptic potential, pEPSP) were recorded at stratum radiatum following stimulation of the stratum fibers. theta pattern primed-bursts were delivered to stratum radiatum and PB potentiation was assessed. The results showed that 48- 144 h after kindling, PB potentiation in CA1 of kindled slices is sign ificantly greater than control slices. In contrast, 30-33 days after k indling PB potentiation was not observed and the pEPSP slope was depre ssed after PBs delivery, which lasted at least 60 min. Our results sug gest that shortly after kindling, PB potentiation can be more readily induced while one month later, it is more difficult to elicit. These f indings may help to explain the behavioral deficits seen with the kind ling model of epilepsy.