(a) Single experiment showing occlusion of LTPGABA with Sp-cAMPS (10μM)-induced potentiation. Sp-cAMPS, a cAMP analog, potentiated GABAA IPSCs and occluded the potentiation induced by HFS. Inset: Averaged GABAA IPSCs recorded before (black) and after 25 minutes in Sp-cAMPS (red) and 20 minutes after HFS (green). Calibration: 10ms, 100 pA.
(b) Averaged experiments showing that Sp-cAMPS mimics LTPGABA (152 ± 10% of pre-drug values, n=5).
(c) After the IPSCs in Sp-cAMPS reached a stable potentiated level, HFS was delivered. Only the portion of the experiment after Sp-cAMPS-induced potentiation is shown. Sp-cAMPS-induced potentiation occluded further potentiation of IPSCs by HFS (100 ± 0.5% of pre-HFS values, n=6).
(d) Bath application of Rp-cAMPS (20 μM), a PKA inhibitor, had no effect on the induction or expression of LTPGABA (control LTP, filled circles: 144 ± 14% of pre-HFS values, n=10; Rp-cAMPS cells, open circles: 128 ± 10% of pre-HFS values, n=6). Rp-cAMPS was present in the bath for at least 15 minutes prior to HFS.