1. Divisions of Pathology and Neuroscience, Hospital for Sick Children, and Departments of Pathology, Toronto, Ontario M5G 1X8, Canada
2. Department of Physiology, University of Toronto, Toronto, Ontario M5G 1X8, Canada

Correspondence to: Y. T. Wang¹ Correspondence and requests for materials should be addressed to Y.T.W. (e-mail: Email: y.t.wang@utoronto.ca).

Abstract

Modification of synaptic strength in the mammalian central nervous system (CNS) occurs at both pre- and postsynaptic sites¹,². However, because postsynaptic receptors are likely to be saturated by released transmitter, an increase in the number of active postsynaptic receptors may be a more efficient way of strengthening synaptic efficacy^{3, 4, 5, 6, 7}. But there has been no evidence for a rapid recruitment of neurotransmitter receptors to the postsynaptic membrane in the CNS. Here we report that insulin causes the type A -aminobutyric acid (GABA_A) receptor, the principal receptor that mediates synaptic inhibition in the CNS⁸, to translocate rapidly from the intracellular compartment to the plasma membrane in transfected HEK 293 cells, and that this relocation requires the 2 subunit of the GABA_A receptor. In CNS neurons, insulin increases the expression of GABA_A receptors on the postsynaptic and dendritic membranes. We found that insulin increases the number of functional postsynaptic GABA_A receptors, thereby increasing the amplitude of the GABA_A-receptor-mediated miniature inhibitory postsynaptic currents (mIPSCs) without altering their time course. These results provide evidence for a rapid recruitment of functional receptors to the postsynaptic plasma membrane, suggesting a fundamental mechanism for the generation of synaptic plasticity.