glucose. The pH was adjusted to 7.4 with NaOH. Spontaneous inhibitory postsynaptic currents (sIPSCs) were recorded at a holding potential of −70 mV in the presence of 20 μM CNQX (Tocris, catalog# 0190) added to the perfusion solution. Miniature inhibitory postsynaptic currents (mIPSCs) were recorded at a holding potential of −70 mV in the presence of 20 μM CNQX and 1 μM tetrodotoxin (TTX; VWR, catalog#89160–628). Inhibitory identity was confirmed via perfusion of 50 μM picrotoxin (PTX; Tocris, catalog# 11–281). The following MOR agonist was used for the sIPSC recordings: DAMGO ([D-Ala2, N-MePhe4, Gly-ol]-enkephalin) (Hellobio, cat# HB2409) 6 μM. All recordings were conducted at room temperature because recordings made at elevated temperatures resulted in poor recording quality and shorter recording durations. Cells were excluded from analysis if series resistance (Rs) changed by more than 20% along the duration of the recording. In addition, any recordings where the access resistance was greater than 25 MΩ was also excluded from the analysis. Electrophysiological data were analyzed using Clampfit 10.5 (Molecular Devices).
