CO₂ Anesthesia in Drosophila — Effects
CO₂ anesthesia is the workhorse of fly genetics. It is fast (knockdown in seconds), cheap (a tank lasts months), and reversible (recovery in 1–5 minutes). But it is not without consequences.
CO₂ acts on the central nervous system through hypercapnic acidosis — the dissolved CO₂ lowers tissue pH, which inhibits synaptic transmission. Recovery requires the CO₂ to diffuse out and the buffering system to restore baseline pH. The process is reversible but not instantaneous.
Climbing performance was significantly impaired for ~24 hours after a 30-min exposure, and remained measurably reduced for some flies even at 48 hours. Flight performance recovered faster but still showed transient deficits. The conclusion: any CO₂ exposure within 24 hours of a behavioral assay is a potential confound.
Schedule any handling that requires CO₂ at least 24 hours before behavioral assays. For high-stakes assays (sleep, aggression), use cold anesthesia or unanesthetized handling instead. Document every CO₂ exposure in your lab notebook so you can audit the cumulative load on every cohort.