Is rapid effect of thyroxine on GABAergic IPSCs purely postsynaptic?

BackgroundThyroid hormones (THs) are well known for their genomic effects but recently several studies revealed their actions as rapid modulators of membrane receptors. In particular, fast thyroxine effect on GABAa receptors have been reported. We addressed question whether presynaptic mechanisms can be also involved in modulation of GABAergic transmission by thyroxine.MethodsUsing patch-clamp technique we examined fast effects of thyroxine (2 μM) onevoked GABAergic postsynaptic currents.ResultsWe found that in addition to the inhibitory effect on IPSC amplitude, thyroxine changed IPSC coefficient of variation (CV).ConclusionThis result suggests involvement of a presynaptic mechanism in thyroxine effect on GABAergic transmission.