Responses to electrical and mechanical stimuli of the epithelium in earthworm giant axons identified by lucifer yellow-CH dye.

The present study shows a correlation between the evoked response and the cell where the response was recorded. The cells in question are the three giant axons, one median giant fiber (MGF) and two lateral giant fibers (LGF), and the responses were evoked by electrical and mechanical stimuli applied to the epithelial surface of an isolated neuromuscular preparation from the earthworm, Amynthas hawayanus. Extra- and intracellular responses were recorded from the ventral nerve cord and from the three giant axons. Lucifer Yellow-CH was injected into the axon simultaneously while recording intracellularly with a Dagan 8,500 high impedance bridge system. The action potentials thus evoked were conducted antero-posteriorly and postero-anteriorly in both types of giant axons. Different latencies were found between the electrically and the mechanically evoked responses and between the responses recorded from the MGF and from the LGF. These differences may be attributed to different neuronal circuits conveying these responses to both giant axons.