Fig. 3.

GABA_ARs but not GABA_BRs mediate the GABA_A-LTP that was partially counteracted by a CB₁R-mediated DSI. (A) Plot of the average peak IPSC amplitude vs. time, showing that the IPSCs and the GABA_A-LTP were abolished by PiTX (50 µM; horizontal shaded bar). The upper values are averaged responses from a representative experiment at time points 1, 2 and 3. (B) Plot as in A, but showing that blockade of GABA_BRs by incubation with CGP55845 (2 μM) did not interfere with the GABA_A-LTP. The upper values are averaged IPSCs from a representative experiment at time points 1 and 2. (C) Plot as in B, but showing that in the absence of both the pulse protocol and ACh, CGP55845 had no effect on IPSCs recorded at −75 mV. (D) Plot as in B, but showing that in the absence of the pulse protocol and ACh, AM-251 (2 µM; horizontal bar) had no effect on IPSCs recorded at −75 mV. (E) Plot as in B, but showing that blockade of CB₁Rs by superfusion with AM-251 (horizontal bar) enhances the GABA_A-LTP. (F) Plots showing the PPR in the six cases (open circles) and the corresponding average (solid circles) computed at the control, 20 min post-Ach, and post–AM-251 in the experiments shown in E.