C and b metabond

For fiber photometry experiments, a single fiber probe (200 μm, Chi Square Bioimaging) was placed and fixed (C and B Metabond, Parkell) 100 μm above the injection site in the LHb. For optogenetic manipulation a single fiber (200 μm, Thorlabs) was placed at the following coordinates (AP: −1.4 mm, L: ± 0.1 mm, V: −2.2 mm). Surgery was performed under isoflurane anesthesia (induction: 4%, maintenance: 1.8–2%, Univentor). For endoscope experiments, mice were anesthetized (as described above) and implanted with a GRIN lens (6.1 mm length, 0.5 mm diameter; Inscopix, #100-000588). The lens was placed ∼150–200 μm above the injection site using the following coordinates from bregma (−1.40 mm AP, 0.45 mm ML, −2.85 to −2.9 mm DV; lowered at a speed of 1 μm/s). A stainless steel headbar was implanted on the skull. To do so, the skull was scraped clean and covered with a layer of Cyanoacrylate glue (Vetbond, 3 M). The headbar was lowered to touch the skull over lambda, then secured to the skull with a layer of dental adhesive (C and B Metabond, Parkell), followed by dental cement (Jetkit, Lang). For pain management, paracetamol (500 mg/250 ml; 200-300 mg/kg/day) was added to the drinking water after the surgery. Proper viral expression and fiber/GRIN lens placement in brain areas of interest were confirmed post hoc using histology for all experiments.

In adult mice, a custom cut square 3 × 3 mm cranial window (#1 coverslip glass) was placed over the cortex of previously electroporated or virally injected mice as described previously (Roth et al., 2020 (link)). Mice were anesthetized using Avertin and the anti-inflammatory drugs Carprofen and Dexamethasone were administered. A craniotomy matching the size of the coverslip was cut using #11 scalpel blades (Fine Science Tools) and the coverslip was carefully placed on top of the dura within the craniotomy without excessive compression of the brain. The window was centered using stereotactic coordinates 3 mm lateral and 1.5 mm posterior from bregma for barrel cortex. The window and skull were sealed using dental cement (C and B Metabond, Parkell). A custom-made metal head bar was attached to the skull during surgery to fixate the mouse for imaging. Mice were allowed to recover for 2–3 weeks after surgery before two-photon imaging.