PT  - JOURNAL ARTICLE
AU  - Mark D. Eyre
AU  - Massimiliano Renzi
AU  - Mark Farrant
AU  - Zoltan Nusser
TI  - Setting the Time Course of Inhibitory Synaptic Currents by Mixing Multiple GABA<sub>A</sub> Receptor α Subunit Isoforms
AID  - 10.1523/JNEUROSCI.6495-11.2012
DP  - 2012 Apr 25
TA  - The Journal of Neuroscience
PG  - 5853--5867
VI  - 32
IP  - 17
4099  - http://www.jneurosci.org/content/32/17/5853.short
4100  - http://www.jneurosci.org/content/32/17/5853.full
SO  - J. Neurosci.2012 Apr 25; 32
AB  - The kinetics of IPSCs influence many neuronal processes, such as the frequencies of oscillations and the duration of shunting inhibition. The subunit composition of recombinant GABAA receptors (GABAARs) strongly affects the deactivation kinetics of GABA-evoked currents. However, for GABAergic synapses, the relationship between subunit composition and IPSC decay is less clear. Here we addressed this by combining whole-cell recordings of miniature IPSCs (mIPSCs) and quantitative immunolocalization of synaptic GABAAR subunits. In cerebellar stellate, thalamic relay, and main olfactory bulb (MOB) deep short-axon cells of Wistar rats, the only synaptic α subunit was α1, and zolpidem-sensitive mIPSCs had weighted decay time constants (τw) of 4–6 ms. Nucleus reticularis thalami neurons expressed only α3 as the synaptic α subunit and exhibited slow (τw = 28 ms), zolpidem-insensitive mIPSCs. By contrast, MOB external tufted cells contained two α subunit types (α1 and α3) at their synapses. Quantitative analysis of multiple immunolabeled images revealed small within-cell, but large between-cell, variability in synaptic α1/α3 ratios. This corresponded to large cell-to-cell variability in the decay (τw = 3–30 ms) and zolpidem sensitivity of mIPSCs. Currents evoked by rapid application of GABA to patches excised from HEK cells expressing different mixtures of α1 and α3 subunits displayed highly variable deactivation times that correlated with the α1/α3 cDNA ratio. Our results demonstrate that diversity in the decay of IPSCs can be generated by varying the expression of different GABAAR subunits that alone confer different decay kinetics, allowing the time course of inhibition to be tuned to individual cellular requirements.