Fig. 2.

The SV cycle functions normally after Baf-produced depletion of vesicular glutamate, as confirmed by the ability to load a normal amount of exogenous GABA into SVs by endocytosis and to release it again by exocytosis. (A) Autaptic EPSC measured at the beginning of the experiment (Left) and after puffing on Baf and stimulating for 10 min at 0.2 Hz to empty glutamate from the SVs (Right). (B) Response of the same cell (after emptying SVs) to a 60-s application of GABA loading solution containing 100 mM GABA. An inward current was produced because the internal solution contained high chloride. (C) Postload IPSC recorded in the same cell as in A and B after washing out the GABA loading solution and blocking any residual EPSC with 20 μM CNQX. This postload IPSC is due to the evoked release of endocytosed GABA onto postsynaptic GABA_A receptors. (D) Amplitude of the postload IPSC, expressed as a percentage of the initial EPSC amplitude (e.g., A Left), for experiments in which SVs were first depleted of glutamate (Baf), or for control experiments in which Baf was not applied (No Baf). The two measures are not significantly different (P = 0.69), suggesting that vesicular endocytosis and exocytosis is unaffected by prior treatment with Baf.