Inhibition of glutamate transporters enhances PN responses to a short high frequency burst of parallel fibre activity. (Ai) A burst of high frequency stimuli to the PFs evoked a large inward current in PNs (high-frequency PF EPSC). 50µM TBOA enhanced both the peak amplitude and the duration of this current, further addition of 0.2 mM MCPG, a type 1 mGluR antagonist significantly reduced the slow component of the high frequency EPSC leaving the peak current unchanged; CNQX, an AMPA-KA receptor antagonist abolished all current. Difference currents (Aii) where the inward currents before and after TBOA, and TBOA and MCPG, are subtracted. Note that in the presence of both TBOA and MCPG a small, slow current (note dashed line) remained, and this current was sensitive to the AMPA receptor antagonist CNQX (Ai). All changes occurred in the absence of any significant changes in input or series resistance of the neuron, scale bar is 100 pA and 10 ms (Aiii). B shows the individual and mean values of the changes in EPSC peak amplitude, duration and amplitude of the slow component of the high-frequency PF EPSC, bars are mean values and error bars are SEM, filled circles show values from individual neurons and connecting grey lines show how the responses changed in individual neurons; control, TBOA, and TBOA and MCPG. (Repeated measures oneway ANOVA, where * and ** represent P < 0.05, P < 0.01 respectively, ns denotes not significant.) C shows the mean difference currents for the same cells as in B. The amplitude and time to peak of the TBOA induced difference currents were unchanged by MCPG (P = 0.53 and 0.28 respectively) but the duration of the current significantly shortened, statistical comparisons used paired T-test, * represents P < 0.05.