RT Journal Article SR Electronic T1 Homeostatic Strengthening of Inhibitory Synapses Is Mediated by the Accumulation of GABAA Receptors JF The Journal of Neuroscience JO J. Neurosci. FD Society for Neuroscience SP 17701 OP 17712 DO 10.1523/JNEUROSCI.4476-11.2011 VO 31 IS 48 A1 Matthew D. Rannals A1 Jaideep Kapur YR 2011 UL http://www.jneurosci.org/content/31/48/17701.abstract AB Mechanisms of homeostatic plasticity scale synaptic strength according to changes in overall activity to maintain stability in neuronal network function. This study investigated mechanisms of GABAergic homeostatic plasticity. Cultured neurons exposed to depolarizing conditions reacted with an increased firing rate (high activity, HA) that normalized to control levels after 48 h of treatment. HA-treated hippocampal neurons displayed an attenuated response to further changes in depolarization, and the firing rate in HA-treated neurons increased above normalized levels when inhibition was partially reduced back to the level of control neurons. The amplitude and frequency of mIPSCs in hippocampal neurons increased after 48 h of HA, and increases in the size of GABAA receptor γ2 subunit clusters and presynaptic GAD-65 puncta were observed. Investigation of the time course of inhibitory homeostasis suggested that accumulation of GABAA receptors preceded presynaptic increases in GAD-65 puncta size. Interestingly, the size of GABAA receptor γ2 subunit clusters that colocalized with GAD-65 were larger at 12 h, coinciding in time with the increase found in mIPSC amplitude. The rate of internalization of GABAA receptors, a process involved in regulating the surface expression of inhibitory receptors, was slower in HA-treated neurons. These data also suggest that increased receptor expression was consolidated with presynaptic changes. HA induced an increase in postsynaptic GABAA receptors through a decrease in the rate of internalization, leading to larger synaptically localized receptor clusters that increased GABAergic synaptic strength and contributed to the homeostatic stabilization of neuronal firing rate.