Simultaneous Neuronal Recordings in Prefrontal Cortex and Hippocampus

After finishing collective testing, animals were allowed to recover ad libitum weight and then were used for electrophysiological recordings. Procedures were similar to what we have previously described (Negrón-Oyarzo et al., 2015 (link); Espinosa et al., 2019a (link),b (link)). We recorded simultaneous neuronal activity in the prefrontal cortex and hippocampus. Animals were anesthetized with urethane (0.8 g/kg dissolved in saline, i.p.) and a mixture of ketamine/xylazine (40 mg/kg ketamine; 4 mg/kg xylazine dissolved in saline, i.p.). Anesthesia was maintained throughout the experiment with urethane administered every 20 min with a bomb when required. During the entire experiment, glucosamine solution (0.5–1 mL) was injected subcutaneously every 2 h to maintain the animal hydrated and body temperature was maintained at 36 ± 1°C using a homeothermic blanket (Harvard Apparatus, MA, United States) and monitored with a rectal probe connected to a temperature controller (Harvard Apparatus, MA, United States). Animals were firmly placed in a stereotaxic frame (Stoelting Co.).