S-100-immunoreactivity in spontaneously active snail neurons.

The distribution of S-100-immunoreactive material was examined in the central nervous system of the gastropod snail. Helix pomatia, and electrophysiological properties of S-100-positive neurons were characterized. Immunocytochemical studies revealed S-100-like protein to be present in neurons localized in the cerebral, left parietal, and visceral ganglia, but not in glial cells. Among the immunoreactive neurons we identified the giant cells LPa3 and LPa4. Western blots showed a single S-100-immunoreactive band at 12-14 kDa. S-100-positive neurons are distinguished by spontaneous discharge activity in a beating or bursting mode and a prominent Ca(2+)-activated potassium outward current. Our result show that a S-100-like protein exclusively present in neurons of the Helix central nervous system is correlated with spontaneous discharge activity of these cells.