Short communicationThe glutamate receptor antagonists CNQX and MPEP decrease fast ripple events in rats treated with kainic acid

- The AMPA/KA receptor antagonist CNQX decreases occurrence of fast ripples.
- The mGluR5 receptor antagonist MPEP decreases fast ripple events.
- There was no effect on fast ripple duration, amplitude or frequency from CNQX/MPEP.
- There is an important contribution of glutamate receptors in fast ripple generation.

Fast ripples (FR) are high frequency oscillations (250-600 Hz) that have been associated with epilepsy. FR are assumed to be generated in small areas of the hippocampus (1 mm3) that contain pathologically interconnected glutamate pyramidal cell clusters. Additionally, a relation between glutamate neurotransmission and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/kainite (AMPA/KA) and metabotropic mGluR5 receptors is well established. Therefore, we hypothesized that antagonism of these glutamate receptors would decrease FR activity. For this propose, we induced status epilepticus with a kainic acid injection in the posterior right hippocampus and performed intracranial EEG recordings to detect and evaluate the presence of FR 15 days after the injection. The glutamate AMPA/KA receptor antagonist CNQX (10 mg/kg) and the mGluR5 antagonist MPEP (20 mg/kg) were administered intraperitoneally, and the effects of the drugs were evaluated for a period of three hours after their administration. The results show a decrease in the number of FR in the first hour after drug administration in both cases (CNQX, p = 0.0125; MPEP, p = 0.0132) and a return to basal values in the third hour of the experiment, but not significant differences in the number of oscillations per event of FR, and the frequency and duration of each event of FR. We therefore conclude that blockade of AMPA/KA and mGluR5 receptors transiently decreases the generation of FR; however, the mechanisms by which this effect is achieved are to be further analyzed in future experiments.