Increased intrinsic excitability and synaptic excitation in the rat hippocampus CAI following cortical contusion head injury

Abstract

Objective To explore electrophysiologic mechanisms underlying posttraumatic epilepsy on the cellular and synaptic level.Methods Whole cell voltage - clamp recordings were used to examine intrinsic excitability and evoked synaptic events from CA1 pyramidal cells in slices prepared from fluid percussion injury (FPI) rat at various times after the brain injury.Results We find that CA1 pyramidal cells in FPI rats show:( 1 ) increased membrane input resistance and time constant,and decreased threshold current of action potential,( 2 ) decreased paired - pulse ratio (PPR) and a shift of paired - pulse facilitation (PPF) to paired - pulse depression (PPD),which may suggest increase of presynapse transmitter release probability. Conclusions These findings suggest that there is trauma - induced increased intrinsic excitability and synaptic excitation on the cellular level in the rat hippocampus CA1 following cortical contusion head injury.These alterations may facilitate the progress towards the development of epilepsy. Key words: Traumatic brain injury;  Epilepsy;  Hippocampus;  Patch clamp;  Synaptic transmission