Fig. 8.

Selective block of GABA and muscimol effects on postsynaptic currents with TPMPA. Traces show PSCs before application (control), during application of 50 μm GABA (A, B) and 0.5 μmmuscimol (C, D), and during coapplication of 50 μm TPMPA with GABA and muscimol. Regardless of whether GABA or muscimol reduced (A, C) or enhanced (B, D) postsynaptic currents at low concentrations, coapplication of TPMPA completely blocked the agonist effect in all cases. Because TPMPA acts as a weak GABA_B receptor agonist, the GABA_B receptor antagonist CGP 52432 was always coapplied with TPMPA. The neuron in A was identified as a stellate cell, and the neuron in C was identified as a horizontal cell. Arrows indicate SO stimulus onset.