The sea urchin, Paracentrotus lividus, as a model to investigate the onset of molecules immunologically related to the α-7 subunit of nicotinic receptors during embryonic and larval development.

Nicotinic acetylcholine receptors play a major role in the regulation of electrochemical synapses at neuromuscular junctions. During the early stages of Paracentrotus lividus development, the nicotinic receptor-like molecules are found and localized by use of the specific blocker, -bungarotoxin, and by α-7 subunit immunoreactivity. Both the methods identify and localize the nicotinic receptor-like molecules at the sites where active changes in ionic intracellular concentration take place. These are well known to lead either fertilization, sperm propulsion or co-ordinated ciliary movement. After neural differentiation, immunoreactivity for the α-7 subunit is localized mainly in ganglia, ectoderm ciliary bands and in the motile cells forming the gut wall. Both α-bungarotoxin binding sites and α-7 subunits are also localized at the cells linked to the skeletal rods, performing the small movements which drive the swimming direction in the water column. The localization of these molecules paves the way to a speculation on their function and possible role in neurogenesis as well as neurodegeneration.