Tandem of P domains in a weak inwardly rectifying K+ channel (TWIK)-related acid sensitive K+-1 channel (TASK-1) is an outwardly rectifying K+ channel that acts in response to extracellular pH. TASK-1 is upregulated in the astrocytes (particularly in the CA1 region) of the hippocampi of patients with temporal lobe epilepsy and chronically epilepsy rats. Since levetiracetam (LEV) is an effective inhibitor for carbonic anhydrase, which has a pivotal role in buffering of extracellular pH, it is likely that the anti-epileptic action of LEV may be relevant to TASK-1 inhibition, which remains to be elusive. In the present study, we found that LEV diminished the upregulated TASK-1 expression in the CA1 astrocytes of responders (whose seizure activities were responsive to LEV), but not non-responders (whose seizure activities were not controlled by LEV) in chronically epileptic rats. ML365 (a selective TASK-1 inhibitor) only reduced seizure duration in LEV non-responders, concomitant with astroglial TASK-1 downregulation. Furthermore, ML365 co-treatment with LEV decreased the duration, frequency and severity of spontaneous seizures in non-responders to LEV. To the best of our knowledge, our findings suggest, for the first time, that the up-regulation of TASK-1 expression in CA1 astrocytes may be involved in refractory seizures in response to LEV. This may be a potential target to improve responsiveness to LEV.
Keywords: ML365; astrocyte; intractable epilepsy; pharmacoresistant epilepsy; refractory seizure.