PT  - JOURNAL ARTICLE
AU  - Matthew D. Rannals
AU  - Jaideep Kapur
TI  - Homeostatic Strengthening of Inhibitory Synapses Is Mediated by the Accumulation of GABA<sub>A</sub> Receptors
AID  - 10.1523/JNEUROSCI.4476-11.2011
DP  - 2011 Nov 30
TA  - The Journal of Neuroscience
PG  - 17701--17712
VI  - 31
IP  - 48
4099  - http://www.jneurosci.org/content/31/48/17701.short
4100  - http://www.jneurosci.org/content/31/48/17701.full
SO  - J. Neurosci.2011 Nov 30; 31
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.