Interface chamber

Tissue was transported from the operating room to the laboratory (located in the same building) in a cold, oxygenated solution containing (in mM) 248 D-sucrose, 26 NaHCO₃, 1 KCl, 1 CaCl₂, 10 MgCl₂, 10 D-glucose, and 1 phenol red, equilibrated with 5% CO₂ in 95% O₂. Neocortical slices of 500 μm thickness were cut with a Leica VT1000S vibratome (Leica GmBH, Wetzlar, Germany, RRID:SCR_016495). They were transferred and maintained at 35–37°C in an interface chamber (Fine Science Tools, Vancouver, BC, Canada) perfused with a standard physiological solution containing (in mM) 124 NaCl, 26 NaHCO₃, 3.5 KCl, 1 MgCl₂, 1 CaCl₂, and 10 D-glucose, equilibrated with 5% CO₂ in 95% O₂.

LTP experiments were performed using an interface chamber (Fine Science Tools). Oxygenated ACSF (95%/5% O₂/CO₂; 120 mM NaCl, 2.5 mM KCl, 2 mM CaCl₂, 1 mM MgCl₂, 1.25 mM NaH₂PO₄, 25 mM NaHCO₃, and 25 mM glucose) warmed to 30°C (TC-324B temperature controller, Warner Instruments) was perfused into the chamber at 1 ml/min. Electrophysiological traces were amplified (Model 1800 amplifier, A-M Systems), digitized and stored (Digidata models 1322A with Clampex software, Molecular Devices). Extracellular stimuli were administered (Model 2200 stimulus isolator, A-M Systems) on the border of area CA3 and CA1 along the Schaffer-collaterals using enameled, bipolar platinum-tungsten (92%:8%) electrodes. fEPSPs were recorded in stratum radiatum with an ACSF-filled glass recording electrode (1–3 MΩ). The relationship between stimulus intensity and fEPSP slopes over various stimulus intensities (0.5–15 V, 25 nA to 1.5 µA) was used to assess baseline synaptic transmission. High-frequency stimulus-induced LTP was induced by administering three 100-Hz tetani (1-s duration) at an interval of 20 s. Synaptic efficacy was monitored 20 min before and 1–3 h following induction of LTP by recording fEPSPs every 20 s (traces were averaged for every 2-min interval).

Extracellular field recordings were performed in 4 adult Dyt1 heterozygous KO mice and 6 matched WT littermate mice as previously described [34 (link), 62 (link)]. Hippocampi were rapidly removed from these adult mice and briefly chilled in ice-cold cutting saline (110 mM sucrose, 60 mM NaCl, 3 mM KCl, 1.25 mM NaH₂PO₄, 28 mM NaHCO₃, 5 mM D-glucose, 500 μM CaCl₂, 7 mM MgCl₂, and 600 μM ascorbate). Transverse slices 400-μm thick were prepared with a Vibratome and maintained at least 45 min in a holding chamber containing 50% artificial cerebral spinal fluid (aCSF; 125 mM NaCl, 2.5 mM KCl, 1.25 mM NaH₂PO₄, 25 mM NaHCO₃, 25 mM D-glucose, 2 mM CaCl₂, and 1 mM MgCl₂) and 50% cutting saline. The slices were then transferred to a recording chamber and perfused (1 ml/min) with 100% aCSF. Slices were allowed to equilibrate for 60–90 min in a Fine Science Tools interface chamber at 30°C. All solutions were continuously bubbled with 95% O₂/5% CO₂.