Electrophysiological Recording of Compound Action Potentials

Compound action potentials (CAPs) in the external capsule were recorded as previously described [20 (link)]. Mice were anesthetized with isoflurane and were decapitated to remove the brains rapidly. A 350-μm brain slices coronal were made using a vibratome (1200s, Leica). Slices were transferred in artificial cerebrospinal fluid (aCSF) saturated with 95% O₂+5% CO₂ mixture at 32°C for 0.5 h and at room temperature for 1 h subsequently for recovery. The aCSF contained 124 mM NaCl, 2.5 mM KCl, 2 mM CaCl₂, 1 mM NaH₂PO₄, 24 mM NaHCO₃, 1.3 mM MgSO₄, and 10 mM d-glucose. A concentric stimulating electrode and a glass microelectrode (5~8 MΩ) were used for stimulating and recording. CAPs were induced by monophase square waves (0.1 ms duration) with the stimulus generator (STG 4002, Multichannel). Signals evoked were amplified by Axoclamp 700B (Molecular Devices) and digitized Axon Digidata 1440A (Molecular Devices).