Anesthetic-like effects of ketamine in C. elegans

Transparency of Caenorhabditis elegans enables microscopic in vivo imaging of cellular processes, but immobilization is required due to high locomotor activity. Here, anesthetic-like effects of dissociate anesthetic ketamine in adult C. elegans are presented using video recordings and infrared-based automated activity tracking. Ketamine caused a reversible blockade of locomotion at a similar concentration (20–50 mM) at which conventionally used immobilizing agent sodium azide (NaN₃) produces paralysis. The levels of immobilization at 20 mM ketamine enabled fluorescent and brightfield imaging. The worms’ locomotory activity recovered fully after ketamine exposure and no acute toxicity was observed. However, a marked chemosensation deficiency was noted immediately after 20 mM ketamine exposure. Short-term ketamine treatment did not show signs of SKN-1 (skinhead-1) activation, a marker of the stress response associated with NaN_3. In sum, our results show ketamine’s potential as a non-toxic nematode immobilizing agent and rationalize C. elegans as a model organism to understand its pharmacology.