Using GLUT-4 antagonist to test the impact of energy constraints on neuronal dynamics and connectivity.

GLUT-4 antagonism by Indinavir causes a significant depolarization in the resting membrane potential of GAD2+ interneurons when compared to untreated neurons, however, this depolarization was not observed in GAD2+ interneurons pretreated with Indinavir and Ketones. Even though the insulin resistant GAD2+ interneurons were in a more depolarized state, we also observed a slight decrease in the spike discharge frequency in response to fixed current inputs, which indicates the cells might be less excitable due to prolonged depolarization or depolarization block. Furthermore, when insulin resistance tissue was treated with ketones, we did not observe a decrease in spike frequency. Our preliminary results suggest that blockade of GLUT-4 will increase the likelihood of the cell to depolarize but not the frequency of firing, which could ultimately change the balance of neural network activity.

To evaluate whether ketones can restore evoked Ca2+ transients in insulin resistant GAD+interneurons, we used acute hippocampal slices from Gad2Cre.GCAMP5TdTomatoe mice and 2-photon microscopy. We demonstrated that Focal KCl (5mM) administration evoked cytosolic Ca2+ increases in the Gad2Cre.GCAMP5TdTomatoe+ cells in control slices, slices pretreated with Indinavir (a specific Glut4 antagonist), and slices pretreated with both Indinavir and Ketones. In the slices pretreated with Indinavir, the mean KCl evoked peak was significantly reduced when compared to untreated control slices. In slices that were pretreated with Indinavir and Ketones, the mean KCl evoked peak was not significantly different from that of the control. Taken together, these data suggest that the impairment of Glut4 on interneuron firing properties can be reversed with the treatment of Ketones.