QUISQUALIC ACID-INDUCED SEIZURES DURING DEVELOPMENT - A BEHAVIORAL AND EEG STUDY

Quisqualic acid (QA) is an excitatory amino acid analogue that binds t o the glutamate ionotropic receptor subclass AMPA (alpha-amino-3 hydro xy-5 methyl-4 isoxazol propionic acid) and metabotropic receptor phosp holipase C. To study its epileptogenic properties, we administered QA through an intraventricular cannula to 23-, 41-, and 60-day-old rats w ith recording electrodes implanted in amygdala, hippocampus, and neoco rtex. The frequency power spectra of the recorded EEG was computed by fast fourier transform (FFT), and coherence between anatomic sites was computed. Seizures occurred in all animals receiving QA. The behavior al manifestations of the seizures varied as a function of age, with yo unger rats demonstrating rigidity and immobility followed by circling activity and intermittent forelimb clonus and 60-day-old animals exhib iting severe, wild running followed by generalized clonus. Ictal elect rical discharges occurred in all animals. Neocortical ictal discharges occurred more prominently in the younger animals, and amygdala ictal discharges were more prominent in the older animals. Marked increases in spectral power occurred during the seizures in all anatomic structu res and at all frequencies. Our results demonstrate that the clinical manifestations of QA seizures vary during development; results of the neurophysiologic studies suggested that neocortex may play an importan t role in genesis of QA seizures in immature brain.