not-yet-known not-yet-known not-yet-known unknown GABAergic current recordings from Xenopus oocytes microtransplanted with human hippocampal brain tissue The procedure of membrane extraction from human hippocampal brain tissues and preparation of Xenopus laevis oocytes and injection procedures have been previously described in detail (Miledi et al., 2006). Briefly, tissues were homogenized with a Teflon glass homogenizer using 2 mL of glycine buffer (composition in mM: 200 glycine, 150 NaCl, 50 EGTA, 50 EDTA, 300 sucrose; plus 20 μL protease inhibitors [P2714; Sigma]; pH 9 adjusted with NaOH). Subsequently, the homogenate underwent two centrifugation cycles, the first at 9500 g for 15 minutes in a Beckmann centrifuge (C1015 rotor; Palo Alto, CA). Afterwards, the supernatant was collected and subjected to a second centrifugation at 105×g for 2 hours in a TL-100 rotor at 4 °C. The pellet was washed, resuspended in assay buffer (glycine 5 mM) and used directly, or aliquoted and stored at −80 °C for later use. From 12 to 48 hours after injection, membrane currents were recorded from voltage-clamped Xenopus oocytes using two microelectrodes filled with 3M KCl. The oocytes were placed in a 0.1 mL recording chamber perfused continuously (9–10 mL/min) with oocyte’s Ringer (OR) containing (mM): 82.5 NaCl; 2.5 KCl; 2.5 CaCl2; 1 MgCl2; 5 Hepes, adjusted to pH 7.4 with NaOH at RT (20–22 °C). GABA (500 µM, diluted from a 100 mM stock solution before each experiment) was applied through a gravity driven multi-valve perfusion system controlled by a digital interface (Biologique RSC 200; Claix, France). In all the experiments, the holding potential was −60 mV.