Systemic injection of kainic acid differently affects LTP magnitude depending on its epileptogenic efficiency

PLoS One. 2012;7(10):e48128. doi: 10.1371/journal.pone.0048128. Epub 2012 Oct 31.

Abstract

Seizures have profound impact on synaptic function and plasticity. While kainic acid is a popular method to induce seizures and to potentially affect synaptic plasticity, it can also produce physiological-like oscillations and trigger some forms of long-term potentiation (LTP). Here, we examine whether induction of LTP is altered in hippocampal slices prepared from rats with different sensitivity to develop status epilepticus (SE) by systemic injection of kainic acid. Rats were treated with multiple low doses of kainic acid (5 mg/kg; i.p.) to develop SE in a majority of animals (72-85% rats). A group of rats were resistant to develop SE (15-28%) after several accumulated doses. Animals were subsequently tested using chronic recordings and object recognition tasks before brain slices were prepared for histological studies and to examine basic features of hippocampal synaptic function and plasticity, including input/output curves, paired-pulse facilitation and theta-burst induced LTP. Consistent with previous reports in kindling and pilocapine models, LTP was reduced in rats that developed SE after kainic acid injection. These animals exhibited signs of hippocampal sclerosis and developed spontaneous seizures. In contrast, resistant rats did not become epileptic and had no signs of cell loss and mossy fiber sprouting. In slices from resistant rats, theta-burst stimulation induced LTP of higher magnitude when compared with control and epileptic rats. Variations on LTP magnitude correlate with animals' performance in a hippocampal-dependent spatial memory task. Our results suggest dissociable long-term effects of treatment with kainic acid on synaptic function and plasticity depending on its epileptogenic efficiency.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Chronic Disease
  • Disease Resistance
  • Electroencephalography
  • Hippocampus / drug effects
  • Hippocampus / pathology
  • Hippocampus / physiopathology*
  • In Vitro Techniques
  • Kainic Acid
  • Long-Term Potentiation / drug effects*
  • Male
  • Presynaptic Terminals / physiology
  • Rats
  • Rats, Sprague-Dawley
  • Rats, Wistar
  • Recognition, Psychology / drug effects
  • Status Epilepticus / chemically induced
  • Status Epilepticus / physiopathology*
  • Status Epilepticus / psychology
  • Synaptic Transmission / drug effects
  • Theta Rhythm

Substances

  • Kainic Acid

Grants and funding

This work was supported by grants from the European Commission under FP7 (MemStick Grant Agreement N° 201600) to LMP and from the Spanish Ministerio de Ciencia e Innovación (MICINN) BFU2009-07989 and PIU081067 to LMP and JMS, respectively. EC is a JAE-Doc fellow from the CSIC JAE Program co-funded by the European Social Fund. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.