Effect of Three Types of Mixed Anesthetic Agents Alternate to Ketamine in Mice

Ketamine is usually used for murine anesthesia in animal experiments with other anesthetics for its sedation and analgesic effects. However, ketamine was categorized as a narcotic drug in Japan on January 1, 2007. After this act came into effect, a narcotic handling license became necessary for using and possessing ketamine. Pentobarbital sodium, which is also used for laboratory animal experiments as Nembutal, is no longer being manufactured. For these reasons, other anesthetic agents that can be used without a license are needed. In this paper, we examined the use of anesthetics other than ketamine and pentobarbital sodium. A combination anesthetic (M/M/B: 0.3/4/5) was prepared with 0.3 mg/kg of medetomidine, 4.0 mg/kg of midazolam, and 5.0 mg/kg of butorphanol. The anesthetics were administered to male ICR mice by intraperitoneal injection. In order to assess anesthetic depth and duration, we stimulated the mice directly after loss of righting reflexes to recovery of these same reflexes and then recorded four parameters-a tail pinch reflex, a pedal withdrawal reflex in the forelimbs, a pedal withdrawal reflex in the hindlimbs, and corneal reflex. Each parameter was scored, and the anesthetic depth, expressed by the total score, was summed. The surgical anesthesia duration of M/M/B: 0.3/4/5 mg/kg was almost identical to the surgical anesthetic duration with a ketamine and xylazine mixture (80-8 mg/kg). These data suggested that mice can be anesthetized by M/M/B: 0.3/4/5 as an alternate to ketamine. We thus can recommend M/M/B: 0.3/4/5 for murine surgical anesthesia.