Metabolic effects of CO 2 anaesthesia in Drosophila melanogaster

Immobilization of insects is necessary for various experimental purposes, and CO(2) exposure remains the most popular anaesthetic method in entomological research. A number of negative side effects of CO(2) anaesthesia have been reported, but CO(2) probably brings about metabolic modifications that are poorly known. In this work, we used GC/MS-based metabolic fingerprinting to assess the effect of CO(2) anaesthesia in Drosophila melanogaster adults. We analysed metabolic variation of flies submitted to acute CO(2) exposure and assessed the temporal metabolic changes during short- and long-term recovery. We found that D. melanogaster metabotypes were significantly affected by the anaesthetic treatment. Metabolic changes caused by acute CO(2) exposure were still manifested after 14 h of recovery. However, we found no evidence of metabolic alterations when a long recovery period was allowed (more than 24 h). This study points to some metabolic pathways altered during CO(2) anaesthesia (e.g. energetic metabolism). Evidence of short-term metabolic changes indicates that CO(2) anaesthesia should be used with utmost caution in physiological studies when a short recovery is allowed. In spite of this, CO(2) treatment seems to be an acceptable anaesthetic method provided that a long recovery period is allowed (more than 24 h).