Dual Effects of Morphine on Spontaneuse Seizure Activity in Mouse Brain Hippocampal Slices

Opiates have complex effects on seizure activity. They have both anti- and proconvulsive effects depending on experimental conditions. The aim of this study was to determine the effects of different doses of morphine and naloxon on spontaneous seizure activity in mouse brain hippocampal slices. Spontaneous epileptic activity in the brain slices of mouse was induced by continuous perfusion of low magnesium artificial cerebrospinal fluid (low -Mg2+ ACSF). Extra cellular recordings were performed in the hippocampal CA1 pyramidal cell layer to account for the effects of the drugs on amplitude, duration and number of the ictal events as well as number of interictal spikes. Application of morphine had a biphasic effect on the recorded spontaneous seizure-like events. In a low concentration (10 µM), morphine decreased seizure activity. Higher morphine concentrations (30 & 100 µM) enhanced seizure activity in an apparent dose-dependent manner. Naloxone, a nonselective opiate antagonist, blocked the proconvulsant action of morphine. The results of this study showed that the effect of morphine on seizure in mouse is dose dependent. In other words, low systemic doses of morphine have anticonvulsant effects while high doses are proconvulsant.