Concentration- and time-dependent behavioral changes in Caenorhabditis elegans after exposure to nicotine.

Nicotine induces profound behavioral responses in the model organism Caenorhabditis elegans. We tested the effect of a broad range of concentrations of nicotine (from 0.001 mM to 30 mM in nematode growth medium) on C. elegans locomotor behavior. We also followed the time-course influence on the sensitivity of C. elegans to nicotine (from 0 min to 300 min). A low concentration (0.001 mM) of this alkaloid causes a reduction of the speed of movement. By contrast, moderate concentrations (0.01 and 0.1 mM) induced acceleration of the mean speed of locomotion of C. elegans. High doses of nicotine (above 1 mM) induced slowing down of the movements and, finally, paralysis. Time-dependent analysis revealed that the stimulating effect of nicotine abolished the slowing down of C. elegans in control experiments after 30 min in the presence of 0.001, 0.1 and 10 mM nicotine. In the presence of 0.1 mM nicotine, the stimulation phase lasted up to 70 min. The evidence indicates that nicotine can have dual effects on the speed of locomotion, which is dependent on differences in its dosage and treatment time.