Figure 5
The mGluR4 (type III) receptor antagonist MPPG specifically prevented the change in paired pulse facilitation (PPF) upon inhibition of glutamate uptake. A shows that application of 50 μM TBOA in the presence of the mGluR4 antagonist MPPG no longer changed the PPF and that PPF was also not significantly changed by 25 μM MPPG alone. The graph shows the individual and mean values of the changes in PPF, bars are mean values and error bars are SEM, filled circles show values from individual neurons and connecting grey lines show response changes in individual neurons. The statistical comparison used a repeated measures oneway ANOVA where ns denotes not significant, F2,23 = 1.1, P = 0.35. Importantly the first EPSC was also unchanged (data not shown) in these experiments, F2,23 = 4.4, P = 0.08. TBOA still increased the time course of the recovery of the second of the pair of EPSCs, consistent with its postsynaptic action independent of the presence of MPPG, mean values changed from 14.7 ± 1.6 ms in control cells, to 14.2 ± 1.5 ms in MPPG alone treated cells to 21.7 ± 3.4 ms in MPPG and TBOA treated cells (F2,23 = 11.8, P < 0.05 repeated measures one way ANOVA). B shows for the same example cell as in A that the amplitude of the 200 Hz EPSC also increased in the presence of TBOA and MPPG, the graph is as for A above with a repeated measures oneway ANOVA where F2,14 = 8.7, P < 0.05 and multiple comparisons where * represents P < 0.05 and ns denotes not significant.