GRIN Lens Implantation

Two 1 mm screws were implanted (AP +1.8, ML −2.5; AP −2.8, ML −0.8) to serve as anchors. A small window of skull was removed by using a 2 mm drill bur, centred at AP −2.1, ML +1.6, and the exposed dura was cleaned with fine tweezers. A 27-gauge blunt needle was used to aspirate cortex to expose the vertical striations of the hippocampal fimbria, with artificial cerebrospinal fluid flowing during the procedure to provide a clear operating field. Using the most posterior point of the edge of the drilled hole (next to lambda side) as a reference, the grin lens (0.25pitch, #64-519, Edmund Optics) was implanted 1.35 mm deep, touching the surface of exposed tissue (Cai et al., 2016). Cyanoacrylate glue was applied surrounding the lens to prevent movement and dental cement was built over the glue for support. The lens was then covered with fast setting silicone adhesive (Dragon Skin^® Series, United States). After the surgery, the animal was injected with carprofen (5 mg/kg) and dexamethasone (0.6 mg/kg, Sigma-Aldrich, United States) intraperitoneally every day for the relief of pain and inflammation, and provided with enrofloxacin water (1:150 dilution, Baytril^®, United States) for one week. Four weeks later, a small metal baseplate was mounted on the animal’s head to support the miniscope, which was locked in the position at the optimal focal distance. Figure 1B shows a mouse with a miniscope.