The Sodium Channel Blocker Tricaine Reduces the Regenerative Capabilities of Lumbriculus variegatus

We studied the regenerative abilities of the California Blackworm (Lumbriculus variegatus) when exposed to the voltage-gated sodium channel blocker tricaine (MS-222). Somatic regeneration of heads and tails following body transection was examined under normal conditions and when worms were placed in 2 different concentrations (300μM, 1mM) of tricaine. Images of regenerating worms were examined for ten days following transection and the degree of regeneration quantified. Regeneration of both new head and tail body segments was reduced in the presence of tricaine. Thus, voltage-gated sodium channels appear to contribute to the regeneration process. Because tricaine is a local anesthetic and commonly used to anesthetize fish and amphibians, we assessed the concentrations of tricaine necessary to interfere with action potential conduction and the production of escape behaviors. The concentrations of tricaine necessary to slow conduction velocities of the giant nerve fibers were 2-3 times the concentrations necessary to affect regeneration. However, the concentrations of tricaine necessary to disrupt two quantifiable escape behaviors, body reversal and helical swimming were approximately 25 to 50 percent of the concentration necessary to disrupt regeneration.