Figure 6. Glutamine prevents fEPSP depression during repetitive stimulation of Layer I cortical afferents.

(a) Bright field image of rat brain slice in which Layer I cortical axons have been transected and separated from on column deeper layers. Positions of stimulating (left) and recording electrode (right; in Layer III where Layer V apical dendrites project) are depicted by line drawings. (b) Representative time course of evoked fEPSP amplitude during continuous 0.2Hz stimulation protocol (upper) and plot of paired fEPSP amplitude measurements at 5 min and 60 min for 5 slices stimulated continuously at 0.2 Hz (lower; student's t-test, no significant difference). (c) Representative time course of evoked fEPSP amplitudes recorded during 0.2 Hz stimulation period during baseline (B), after 4^th (4) and 13^th (13) HFS iteration, and during recovery (R) with sample traces above (black trace, aCSF; green trace, glutamine). Summary of fEPSP amplitude after each HFS iteration (right panel; n=5, 2-way repeated measures ANOVA with Bonferroni post test, ***p<0.001, error bars represent 95% CI). (d) As in (c) with slices preincubated with glutamine synthetase inhibitor MSO.