Fig. 5: CR reduces glutamate spillover.
a A scheme illustrating the effect of ionotropic receptor blockers on synaptically induced astrocytic current. Presynaptically released glutamate triggers transient current mediated by astrocytic transporters (IGluT) but does not trigger K+ efflux through postsynaptic AMPA and NMDA receptors. Only a small IK mediated by K+ exiting through K+ channels in the course of an action-potential propagation is recorded in astrocyte. b The protocol to estimate activity-dependent changes in IGluT. Left, astrocytic currents induced by a single stimulus in the presence of ionotropic receptor blockers before (violet trace) and after (black trace) application of glutamate transporter blocker (TBOA). Middle, the astrocytic current induced by five stimuli (black trace, 5 × 50 Hz) superimposed over the astrocytic current induced by four stimuli (orange trace, 4 × 50 Hz). Right, the current to fifth stimulus isolated by subtraction of the current to four stimuli from the current to five stimuli. Superimposed current (violet) is a tail-fit current in response to a single stimulus in the presence of TBOA. IGluT(1) and IGluT(5) were isolated by subtraction of this TBOA-insensitive current. c Representative transporter currents to a single stimulus (IGluT(1), dark traces), and fifth stimulus (IGluT(5), light traces) in control (gray) and CR mice (green). d The summary plot showing similar IGluT(5)/IGluT(1) ratio in control and CR mice. Gray diamonds—control, green diamonds—CR mice. e The summary plot is showing a decrease in τdecay IGluT(5)/τdecay IGluT(1) ratio in CR mice. Gray diamonds—control, green diamonds—CR mice. f Representative western blots of the mouse hippocampus homogenates stained with antibodies against β-actin, GS, and GLT-1. g Normalized protein levels of GLT-1. Gray diamonds—control, green diamonds—CR mice. h Normalized protein levels of GS. Gray diamonds—control, green diamonds—CR mice. The data are presented as mean ± SEM; NS. p > 0.05; *p < 0.05; two-sample t-test.
