Pentobarbital-induced sleep test

The pentobarbital-induced sleep test was performed with a slight modification to a previous report (12). Briefly, mice were administered with pentobarbital sodium (50 mg/kg, i.p.) to induce sleep. The latency of the loss of the righting reflex after pentobarbital administration (“onset” time) and the total sleeping time (the time between the loss and the recovery of the righting reflex, “duration”) were determined for each mouse. The mouse was considered awake if it could right itself (return to the upright position). The time between the loss and recovery of the righting reflex was defined as sleep time. The entire process of the test was recorded using a digital video recorder for analysis.