Optogenetic Modulation of Focal Seizures

Abstract

Abstract Optogenetics rests on the activation of light-gated ion channels or pumps in transgenic animals, and it is used to reversibly excite or silence specific neuronal populations, with millisecond precision and with a higher spatial accuracy than electrical stimulation. To date, epilepsy researchers have used optogenetics to study this neurological disorder, and in particular focal seizures that originate from a discrete brain area as in mesial temporal lobe epilepsy. Here, we will review findings obtained by employing optogenetics in in vitro and in vivo models of focal epileptiform synchronization. We will also address the use of this technique to control acute and chronic spontaneous seizures induced by the administration of chemoconvulsants in animal models of mesial temporal lobe epilepsy, such as the kainic acid and the pilocarpine model. These findings reveal that optogenetic activation or inhibition of excitatory or inhibitory cells can exert paradoxical effects on seizure occurrence depending on the frequency and timing of light stimulation, as well as on the targeted neuronal populations. We also consider the limitations associated with the use of optogenetics and the potential issues that must be solved before this approach is translated to human application. We conclude that optogenetics, despite some limitations, represents an innovative and promising approach to improve our understanding of brain function in health and disease.