The l-AP4-induced inhibition of transmission at the striatopallidal synapse is absent in mGluR4 knock-out mice. A, Representative traces and time course of an experiment from wild-type 129X/SvJ mice illustrating the inhibitory effect of l-AP4 at their striatopallidal synapse. Interestingly, this effect is completely absent in mice lacking mGluR4 (B), suggesting that this receptor underlies the group III mGluR-mediated modulation of transmission at the striatopallidal synapse. C, Summary graph representing mean ± SEM data from control and knock-out mice. *Significant effect of l-AP4, p < 0.01; n = 5 cells per condition.