Attenuated single neuron and network hyperexcitability following microRNA-134 inhibition in mice with drug-resistant temporal lobe epilepsy

The multi-factorial pathophysiology of acquired epilepsies lends itself to a multi-targeting therapeutic approach. MicroRNAs (miRNA) are short noncoding RNAs that individually can negatively regulate dozens of protein-coding transcripts. Previously, we reported that central injection of antisense oligonucleotides targeting microRNA-134 (Ant-134) shortly after status epilepticus potently suppressed the development of recurrent spontaneous seizures in rodent models of temporal lobe epilepsy. The mechanism(s) of these anti-seizure effects remain, however, incompletely understood. Here we show that intracerebroventricular microinjection of Ant-134 in male mice with pre-existing epilepsy caused by intraamygdala kainic acid-induced status epilepticus potently reduces the occurrence of spontaneous seizures. Recordings from ex vivo brain slices collected 2-4 days after Ant-134 injection in epileptic mice, detected a number of electrophysiological phenotypic changes consistent with reduced excitability. Specifically, Ant-134 reduced action potential bursts after current injection in CA1 neurons and reduced excitatory post-synaptic current frequencies in CA1 neurons. Ant-134 also reduced general network excitability, including attenuating pro-excitatory CA1 responses to Schaffer collateral stimulation in hippocampal slices from epileptic mice. Together, the present study demonstrates inhibiting miR-134 reduces single neuron and network hyperexcitability in mice and extends support for this approach to treat drug-resistant epilepsies. Significance statement Temporal lobe epilepsy is one of the most common forms of drug-resistant epilepsy. Identifying molecular regulators of enduring states of hyperexcitability may lead to new therapeutic approaches. MicroRNAs are short noncoding RNAs that act post-transcriptionally to lower levels of sets of protein-coding genes. Here we show that inhibiting miR-134 reduces spontaneous seizures in mice with active epilepsy. Electrophysiologic recordings from brain slices collected when mice were transitioning to fewer seizures revealed changes to both single neuron and inter-regional communication properties that may explain the reduction in hippocampal network excitability. The findings support the development of this microRNA-targeting approach for epilepsy.