Pedal wave recovery following transection of pedal nerves in the slug, Limax maximus.

Abstract

AbstractThe giant garden slug, Limax maximus, crawls by producing sequential pedal waves that propagate forward along a medial band of muscle running the full length of the foot. Nerves that originate in the pedal ganglion appear to innervate the foot musculature along its length, but not all seem to be essential for the initiation and maintenance of pedal wave activity. When nerves running backward from the pedal ganglion were transected, the portion of the sole posterior to the cut initially showed no pedal waves, and pedal waves anterior to the cut showed reduced wave velocity and frequency. After 3 to 21 days, depending primarily on how anterior the transection, fully‐formed pedal waves reappeared in the denervated region of the sole. Waves were propagated along the entire foot, but their velocity and frequency remained lower than found in normal animals or in sham‐operated controls. Methylene blue staining, and electrical stimulation and recording failed to reveal evidence of reinnervation in animals that had recovered full‐foot pedal wave activity. The results suggest that coordinated pedal waves can be maintained on parts of the sole that lack direct connections with the CNS by spread of excitation through the peripheral plexus of the foot.