The effect of spontaneous seizures on pentylenetetrazole and maximum electroshock induced seizures in the Mongolian gerbil.

The seizure sensitive Mongolian gerbil, a genetic model of epilepsy, has been used to investigate the effects of prior spontaneous seizures on the threshold for pentylenetetrazole (PTZ) and maximum electroshock (MES) induced convulsions. In animals which had spontaneous epileptic seizures prior to testing the threshold for PTZ induced convulsions was raised compared to non-seized animals. This inhibitory effect of a spontaneous seizure was not observed for MES convulsions. Pretreatment with naltrexone, an opioid antagonist, attenuated the post-ictal inhibitory effect on PTZ induced convulsions. It is concluded that a spontaneous seizure in the epileptic gerbil leads to non-specific post-ictal inhibition of seizure sensitivity. Endogenous opioids may exert a modulatory action in mediating this phenomenon.