CLUSTERED VOLTAGE-GATED NA+ CHANNELS IN APLYSIA AXONS

Clustering of voltage-gated Na+ channels is critical for the fast salt atory conduction of action potentials in vertebrate myelinated axons. However, the mechanisms responsible for the generation and maintenance of Na+ channel clustering are not well understood. In this study we h ave raised an antibody against the cloned SCAP-1 voltage-gated Na+ cha nnel of the marine invertebrate Aplysia californica and used it to exa mine Na+ channel localization in Aplysia ganglia and in cultured Aplys ia sensory neurons. Our results show that there is a large cytoplasmic pool of Na+ channels in the soma of Aplysia neurons. Furthermore, we show that Na+ channels in Aplysia axons are not homogeneously distribu ted but, rather, are present in distinct clusters. Theoretical conside rations indicate that Na+ channel clustering may enhance action potent ial conduction. We propose that clustered Na+ channels may be a fundam ental property of many axons, and perhaps of many membranes that condu ct Na+-dependent action potentials.