General anesthesia in newborn rodents for experimental microsurgery of theear

Background: Experimental investigations on laboratory animals usually requi re sufficient anesthesia with adequate analgesia and sedation. The techniqu e used should be reliable and easily controllable by the investigator. Here , we present a technique for anesthesia to facilitate invasive and noninvas ive investigations in newborn rats and mice. Methods: Using a custom made b reathing mask, anesthesia was induced in these animals with inhalation of g aseous nitrous oxide-oxygen (equal volume at 1 l/min) and halothane (3 % by volume). To maintain anesthesia, halothane insufflation was reduced to 1-1 .5% by volume. After completion of the experimental procedure, the applicat ion of the inhalative gases was determined and substituted by oxygen at 2 l /min. Anesthesia was performed in spontaneously breathing animals. Heart fr equency and oxygenation were monitored using a commercially available pulse oximeter. Results: Using the above described technique in neonatal rodents , microsurgery of the ear was performed without signs of pain or major blee ding. Auditory brain stem responses were recorded clearly and reproducible. Conclusions: This method represents a noninvasive, well tolerated and easy controllable anesthetic procedure which has proven to provide a sufficient and reliable sedation in neonatal rodents for surgical and nonsurgical inv estigations.