Pre-synaptic and post-synaptic A-type K channels regulate glutamatergic transmission and switching of the network into epileptiform oscillations.

Background And Purpose: Anticonvulsants targeting K channels have not been clinically available, although neuronal hyperexcitability in seizures could be suppressed by activation of K channels. Voltage-gated A-type K channel (A-channel) inhibitors may be prescribed for diseases of neuromuscular junction but could cause seizures. Consistently, genetic loss of function of A-channels may also cause seizures. It is unclear why inhibition of A-channels, compared with other types of K channels, is particularly prone to seizure induction. This hinders the development of relevant therapeutic interventions.

Experimental Approach: Mechanisms underlying epileptogenesis with A-channel inhibition and antiepileptic actions of A-channel activation were investigated with electrophysiological, pharmacological, optogenetic, and behavioral approaches.

Key Results: Pre-synaptic K 1.4 and post-synaptic K 4.3 A-channels act synergistically to gate glutamatergic transmission and control rhythmogenesis in the amygdala. The interconnected neurons set into the oscillatory mode by A-channel inhibition would reverberate with regular paces and the same top frequency, demonstrating a spatio-temporally well-orchestrated system with built-in oscillatory rhythms normally curbed by A-channels. Accordingly, selective over-excitation of glutamatergic neurons or inhibition of A-channels can induce behavioural seizures, which may be ameliorated by A-channel activators (e.g. NS-5806) or AMPA receptor antagonists (e.g. perampanel).

Conclusion And Implications: Trans-synaptic voltage-dependent A-channels serve as a biophysical-biochemical transducer responsible for a novel form of synaptic plasticity. Such a network-level switch into and out of the oscillatory mode may underlie a wide scope of telencephalic information processing or, at its extreme, epileptic seizures. A-channels thus constitute a potential target of antiepileptic therapy.