5-HT and OA enhance action potential-mediated transmitter release of the inhibitor.A, Time courses of peak IPSGs enhanced by 100 nm 5-HT (A₁ ) and 2.5 μm OA (A₂ ). Peak IPSGs were normalized to the average IPSG measured 5 min before the modulators were applied. Insets in A₁ andA₂ , Control (1 and dashed line) and enhanced (2 and solid line) IPSPs that represent the averages of 60 and 75 trials, respectively. ΔE_Cl andR_m measured before and after 5-HT was applied were 9 mV, 0.45 MΩ and 8.3 mV, 0.4 MΩ, respectively. ΔE_Cl and R_mmeasured before and after OA was applied were 10 mV, 0.6 MΩ and 10 mV, 0.7 MΩ, respectively. B, Averaged time courses showing the effects of 5-HT (n = 12) and OA (n = 5) on IPSG amplitude. Open triangles in B₂ represent averaged results (n = 5) from control experiments in which perfusion was stopped but in which no OA was added. All experiments were performed at 23°C.