Differential blocking action of synthetic omega-conotoxin on components of Ca2+ channel current in clonal GH3 cells.

The effect of synthetic omega-conotoxin on two types of Ca2+ channels in clonal rat pituitary cells (GH3) was studied using the whole-cell variant of the patch-clamp technique. Low concentration of omega-conotoxin (50 nM) was sufficient to block a long-lasting Ca2+ channel current but a much higher concentration (1 microM) had little effect on a different type of Ca2+ channel current, which was activated at relatively more negative voltages and showed marked inactivation. The synthetic toxin preferentially targeted a specific type of Ca2+ channel and might provide a unique and powerful tool for studying the molecular properties of Ca2+ channels and the functional role in the process of hormonal secretion.