Electrophysiological Recordings in Anesthetized Rats

Animals were deeply anesthetized with urethane (1.5 g/kg, i.p.) and mounted on a stereotaxic frame (Kopf Instruments). A homoeothermic control system kept the core temperature at 37.5–38°C. Animals were intubated and breathed O₂-enriched room air spontaneously. Physiological parameters were collected throughout the experiments using PhysioSuite (Kent Scientific) and CapStar-100 (CWE). Data used in this report were obtained from animals exhibiting physiological levels of oxygen saturation (> 95%), heart rate (350–450 beats/min), and end-tidal CO₂ (3.5–4.5%). Two separate craniotomies were made. One was used to expose the left transverse sinus and the posterior part of the superior sagittal sinus, including the adjacent cranial dura, extending ~2 mm rostral to the transverse sinus. Another small craniotomy (1 × 1 mm) was made over the right hemisphere, centered 2 mm caudal and 2 mm lateral to Bregma, to allow insertion of the recording electrode into the left trigeminal ganglion. A small burr hole (diameter, 0.5 mm) was drilled above the frontal cortex to induce CSD (Zhao and Levy, 2018a (link)). The exposed dura was bathed with a modified synthetic interstitial fluid (SIF) containing 135 mM NaCl, 5 mM KCl, 1 mM MgCl₂, 5 mM CaCl₂, 10 mM glucose, and 10 mM HEPES, pH 7.2. In all experiments, SIF was used as the vehicle.