Answer: An action potential was always seen at R1.
Which of the following occurred in the presence of tetrodotoxin?

Tetrodotoxin (TTX) is a potent neurotoxin. Its name derives from Tetraodontiformes an order that includes pufferfish porcupinefish ocean sunfish and triggerfish; several of these species carry the toxin. Although tetrodotoxin was discovered in these fish and found in several other animals (e.g. in blue-ringed octopus rough-skinned newts and moon snails) it is actually produced by certain infecting o…

Tetrodotoxin (TTX) is a potent neurotoxin. Its name derives from Tetraodontiformes an order that includes pufferfish porcupinefish ocean sunfish and triggerfish; several of these species carry the toxin. Although tetrodotoxin was discovered in these fish and found in several other animals (e.g. in blue-ringed octopus rough-skinned newts and moon snails) it is actually produced by certain infecting or symbiotic bacteria like Pseudoalteromonas Pseudomonas and Vibrio as well as other species found in animals . Tetrodotoxin is a sodium channel blocker. It inhibits the firing of action potentials in neurons by binding to the voltage-gated sodium channels in nerve cell membranes and blocking the passage of sodium ions (responsible for the rising phase of an action potential) into the neuron. This prevents the nervous system from carrying messages and thus muscles from contracting in response to nervous stimulation. Its mechanism of action selective blocking of the sodium channel was shown definitively in 1964 by Toshio Narahashi and John W. Moore at Duke University using the sucrose gap voltage clamp technique.

Apart from their bacterial species of most likely ultimate biosynthetic origin (see below) tetrodotoxin has been isolated from widely differing animal species including: • all octopuses and cuttlefish in small amounts but specifically several species of the blue-ringed octopus including Hapalochlaena maculosa (where it was called "maculotoxin")

Apart from their bacterial species of most likely ultimate biosynthetic origin (see below) tetrodotoxin has been isolated from widely differing animal species including: • all octopuses and cuttlefish in small amounts but specifically several speci...

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