Characterization of Stimulation-Induced Volume Changes in the Ca1 Region of Rat Hippocampus Slices

Intrinsic optical signals (IOS) were used to evaluate volume regulation mechanisms during Schaffer collateral stimulation-induced volume changes in hippocampal slices. The effects of stimulation frequency, synaptic function, ionotropic glutamate receptor (iGluR) activation, glutamate uptake, and volume regulatory anion channels (VRAC) were examined with IOS. Data were analyzed using ANOVA with Dunnett\u27s post hoc test (p\u3c0.05 indicated significance). IOS changes were stimulation frequency dependent between 1 Hz and 10 Hz with full recovery of IOS within 5 min. Synaptic blockage reduced the rate of swelling by 81% compared to the control and the IOS did not fully recover. Recovery rate was reduced with iGluR inhibition. Inhibition of glutamate uptake reduced the rate of swelling by 70% compared to vehicle controls. During stimulation, action potentials, iGluR activation, and glutamate uptake contribute to swelling. Regulatory volume mechanisms during stimulation were glutamate-mediated via iGluRs and VRAC independent