Activation of group I mGluRs increases the frequency of spontaneous GABAergic input to mitral cells. Voltage clamp recordings (HP = 0 mV) of mitral cells show that the group I mGluR agonist, DHPG, dose-dependently increased the frequency of GABAergic sIPSCs (A) and mIPSCs (C); gabazine eliminated all IPSCs, as shown in lower traces. sIPSCs were recorded in normal ACSF (Control) and mIPSCs were recorded in the presence of CNQX (10 μM), APV (50 μM), and TTX (1 μM). (B and D) Group data showing the dose–response relationship for DHPG effects on sIPSC (n = 6) and mIPSC (n = 7) frequency and amplitude (inset bar graphs) recorded in a 1-min epoch. *P < 0.05 compared with control, ANOVA followed by Neuman–Keuls post-hoc comparisons. DHPG did not affect the amplitude of sIPSCs or mIPSCs. Adapted from Ref. 37.