Frog poison. Batrachotoxin (BTX) is a steroidal alkaloid from the skin of Phyllobates terribilis, a poisonous Colombian frog (the source of the poison used on blowgun darts). In the presence of BTX,...

Extracted text: Frog poison. Batrachotoxin (BTX) is a steroidal alkaloid from the skin of Phyllobates terribilis, a poisonous Colombian frog (the source of the poison used on blowgun darts). In the presence of BTX, Na+Na* channels in an excised patch stay persistently open when the membrane is depolarized. They close when the membrane is repolarized. Which transition is blocked by BTX?