Reduction in focal ictal activity following transplantation of MGE interneurons requires expression of the GABAA receptor α4 subunit.
Despite numerous advances, treatment-resistant seizures remain an important problem. Loss of neuronal inhibition is present in a variety of epilepsy models and is suggested as a mechanism for increased excitability, leading to the proposal that grafting inhibitory interneurons into seizure foci might relieve refractory seizures. Indeed, transplanted medial ganglionic eminence interneuron progenitors (MGE-IPs) mature into GABAergic interneurons that increase GABA release onto cortical pyramidal neurons, and this inhibition is associated with reduced seizure activity. An obvious conclusion is that inhibitory coupling between the new interneurons and pyramidal cells underlies this effect. We hypothesized that the primary mechanism for the seizure-limiting effects following MGE-IP transplantation is the tonic conductance that results from activation of extrasynaptic GABAA receptors (GABAA-Rs) expressed on cortical pyramidal cells. Using in vitro and in vivo recording techniques, we demonstrate that GABAA-R α4 subunit deletion abolishes tonic currents (Itonic) in cortical pyramidal cells and leads to a failure of MGE-IP transplantation to attenuate cortical seizure propagation. These observations should influence how the field proceeds with respect to the further development of therapeutic neuronal transplants (and possibly pharmacological treatments).
C.V. Starr Laboratory for Molecular Neuropharmacology, Department of Anesthesiology, Weill Cornell Medical College New York, NY, USA.
Manoj K
MK
Jaiswal
Department of Pediatrics, Weill Cornell Medical College New York, NY, USA.
Sotirios
S
Keros
Department of Neurological Surgery, Weill Cornell Medical College New York, NY, USA ; Brain and Mind Research Institute, Weill Cornell Medical College New York, NY, USA.
Mingrui
M
Zhao
Brain and Mind Research Institute, Weill Cornell Medical College New York, NY, USA.
Melis
M
Inan
Department of Neurological Surgery, Weill Cornell Medical College New York, NY, USA ; Brain and Mind Research Institute, Weill Cornell Medical College New York, NY, USA.
Theodore H
TH
Schwartz
Department of Psychiatry, Children's Hospital of Philadelphia, University of Pennsylvania School of Medicine Philadelphia, PA, USA.
Stewart A
SA
Anderson
Department of Anesthesiology, University of Pittsburgh Pittsburgh, PA, USA.
Gregg E
GE
Homanics
C.V. Starr Laboratory for Molecular Neuropharmacology, Department of Anesthesiology, Weill Cornell Medical College New York, NY, USA.
Peter A
PA
Goldstein
GABAA receptor; cortex; epilepsy; extrasynaptic; interneuron; α4 subunit