Whole-cell voltage-clamp recordings of substantia gelatinosa neurons

The SG was easily discernible with transmitted illumination as a relatively translucent band across the dorsal horn in the transverse slice preparations (Fig. 1). Blind whole-cell voltage-clamp recordings were made from SG neurons, as previously described [17 (link),19 (link)]. The patch pipettes were filled with a solution containing potassium gluconate solution (in mM): K-gluconate 135, KCl 5, CaCl₂ 0.5, MgCl₂ 2, EGTA 5, HEPES 5, and ATPMg 5 (pH 7.2). The tip resistance of the patch pipettes was 6–12 MΩ. Series resistance was assessed according to the response to a 5-mV hyperpolarizing step. This value was monitored during the recording session, and data were rejected if values changed by >15%. Signals were acquired with a patch-clamp amplifier (Axopatch 700A, Molecular Devices, Union City, CA, USA). The data were digitized with an AD/DA converter (Digidata 1321A, Molecular Devices), stored on a personal computer using a data acquisition program (Clampex, version 9.0, Molecular Devices), and analyzed using a software package (Clampfit, version 9.0, Molecular Devices) (Fig. 1). Cell recordings were obtained in voltage-clamp mode at holding potentials of -70 mV to record EPSCs [17 (link),19 (link)].