Current Study of the Mechanism of Action of the Potential Anti-Epileptic Agent Q808.

Our previous study showed that the anticonvulsant Q808 might be effective against seizures induced by maximal electroshock, pentylenetetrazole (PTZ), isoniazid (ISO), thiosemicarbazide (THIO), and 3-mercaptopropionic acid (3-MP). In the present study, we explored the possible mechanism of action of Q808. Results obtained with high-performance liquid chromatography (HPLC) suggest that Q808 may affect neurotransmitter content in the brain, by specifically increasing GABA content in the rat hippocampus at doses of 40 mg/kg and 80 mg/kg, and by reducing the content of glutamate and glutamine in the rat thalamus at a dose of 80 mg/kg. Intriguingly, there were no changes in the neurotransmitter content in the cortex in response to Q808. In vitro brain slice electrophysiological studies showed that 10-5 M Q808 enhanced the frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) in corn cells of the CA1 area of the hippocampus, and had no effect on the amplitude of sIPSCs, the frequency and amplitude of spontaneous excitatory postsynaptic currents (sEPSCs), or γ-aminobutyric acid (GABA) receptor-mediated currents in primary cultured hippocampal neurons. These findings suggest that the antiepileptic activity of Q808 may be due to its ability to increase the amount of GABA between synapses, without affecting the function of GABA receptors.