C12h22o11

Flies were glued on a plastic slide using a biocompatible dental glue (3 M ESPE Protemp) and pierced in the center, without any prior anesthesia. An alignment wire was used to maintain the Drosophila head in a correct position. The orientation of the head was adapted to the area of interest to be imaged so as to minimize the thickness of tissue the light must travel through.
Next, Drosophila heads were opened using very fine scalpels to remove a rectangular cuticle region (300 µm × 400 µm) covering the brain. The underlying fat tissue was pushed to the corners of this window, and the tracheae were cut and pushed aside to obtain a clear view of the brain. In general, all actions must be performed extremely carefully so as not to damage the glial cells that surround the brain, as well as the MB itself. All microsurgery was performed in the presence of a physiological fluid (Ringer’s solution) to preserve the brain. The composition of this aqueous solution is as follows: 130 mM NaCl, 5 mM KCl, 2 mM MgCl₂, 2 mM CaCl₂, 36 mM C₁₂H₂₂O₁₁ (sucrose), and 5 mM HEPES-NaOH (Sigma-Aldrich). The pH of the solution is 7.3^{18 (link)}.

Calcium hydride granules [CaH₂, 92%, Alfa Aesar, England], acetic acid [CH₃COOH, 99.9%, DAEJUNG Chemical & Metals Co., Ltd., South Korea], sucrose powder [C₁₂H₂₂O₁₁, 99.5% up, Sigma-Aldrich, St. Louis, MO, USA], ammonium chloride [NH₄Cl, 99.99%, Sigma-Aldrich], anhydrous methanol [CH₃OH, 99.9% up, Sigma-Aldrich], and acetone [CH₃COCH₃, 99.9% up, Sigma-Aldrich] were utilized as raw materials. Distilled water was produced and used from a reverse-osmosis system [RO2000, Nexpure®]. All chemicals were used as is without further purification.

A SPEX ball mill (ball diameter 5
mm) was used to combine 10 mmol of V₂O₅ (Sigma-Aldrich,
98% purity), 30 mmol of NaH₂PO₄·2H₂O (Sigma-Aldrich, 99% purity), and 2.5 g of sugar (C₁₂H₂₂O₁₁, Merck, >99%) in a stainless steel
vessel
for 2 h at 1000 rpm.^{33 (link)} The mixture was
then compacted into pellets (13 mm diameter, 1.5 mm thickness) by
being calcined in argon atmosphere for 24 h at 800 °C.