Ca²⁺ channel activating action of maitotoxin in cultured brainstem neurons

The actions of maitotoxin were studied using cultured brainstem cells and adrenal chromaffin cells. Maitotoxin induced a profound increase in the Ca²⁺ influx into cultured brainstem cells after a brief lag period. The maitotoxin-induced Ca²⁺ influx was suppressed by various voltage-dependent Ca²⁺ channel blockers such as Co²⁺, Mn²⁺, verapamil and diltiazem. Maitotoxin-catecholamine release in brainstem cells initiated to increase after a lag period of about 1 min and the increase continued even at 4 min after treatment, while in the adrenal chromaffin cells the release started after an about 1-min lag period to attain a maximum within first 2-min and gradually decrease thereafter. These results suggest that maitotoxin acts on Ca²⁺ channels to increase the Ca²⁺ influx, accompanied by enhancement of catecholamine release in the brainstem cells with a different temporal profile from that in the adrenal chromaffin cells.