Chemical Kindling Enhances Paired-Pulse Index in CA1 Cell Body Layer of Hippocampus of Anesthetized Rats

Kindling epilcptigcnesis was induced by repeated administrations of the chemical convulsant pentylenetetrazol (PTZ). The progressive nature of the chemical kindling was demonstrated by a detailed description of the behavioral sings in the course of the kindling acquistion. The changes of Paired-Pulse Index (PPI) were primariliy investigated with extracellular recording in stratum pyramidale following stimulation of Schaffer collaterals in the CAl region of hippocampus of the PTZ-Kindled and the control rats. The results were as follow: (1) in most of the kindled rats theIirst stimulus evoked a double population spike at moderate and high stimulus. intensities: (2) 4X-1 XX hours alter the kindling no significant difference was observed between the control and the kindled rats, and (3) 30-33 days after the kindling PPI was increased in the kindled rats at IPI of 10 and 20 ms with low and moderate stimulus intensities as compared with the control ones. It seems that an increase in PPJ may be resulted from an enhancement of excitatory synaptic transmission and/or an increase in intrinsic excitability of pyramidal neurons of hippocampal CAl.