Fig. 1
Insulin and pioglitazone treatment effects on the E/I ratio in WT brain slices. a–c Membrane depolarization characteristically leads to regular spiking of layer IV excitatory neurons. This characteristic is evident in control (WT) slices, and after application of insulin (WT I), or insulin + pioglitazone (WT I + P). d EPSP-IPSP sequence following VB stimulation. At − 60 mV, the IPSP does not hyperpolarize below − 60 mV (upper trace). The IPSP polarity reverses at − 80 mV, around GABAA receptor reversal potential (lower trace). e 500 nM insulin application results in an increase of IPSP that hyperpolarized below base line at − 60 mV (upper trace). The IPSP is mediated by GABAA receptor, because it reverses at − 80 mV (lower trace). f Addition of pioglitazone to insulin application does not lead to any notable change. g–i Representative records of GABAA receptor- and AMPA receptor-mediated currents under control, insulin, and insulin + pioglitazone application conditions. HP holding potential. j The averaged AMPA/GABA (E/I) ratios under the three conditions. Note that insulin application significantly reduces the E/I ratio; addition of pioglitazone does not change insulin effects alone. k Box and whisker plots showing the population distribution