Tetrodotoxin
Tetrodotoxin (TTX)
• Low molecular weight neurotoxin.
• Blocks pore region of voltage-gated sodium
channels.
• Prevents propagation of action potentials.
• Death due to asphyxiation.
• Found in a wide array of taxa.
Voltage-gated Na Channels
Voltage-gated Na Channels
Back to neuromuscular junctions!
TTX Resistant Na Channels
TTX
• As little as 1 mg can kill an adult human.
• Newts vary in their toxicity from 0 -16 mg TTX.
• Snakes can vary in resistance levels as well.
Some are not resistant at all, while others can
handle enough TTX to kill over 900 humans!!
TTX as an Antipredator Mechanism
• Snake-newt coevolution
(e.g. Brodie and Brodie
1990, 1991).
• High concentrations of
TTX in skin extracts
(Hanifin et al., 1999).
• Newts with high levels of
TTX are more likely to
survive encounters with
predators (Williams et
al., 2010).
Today’s lab
• We will go down to my lab and race snakes
that have been injected with TTX.
• Please be respectful of the animals!!!!! Do
not tease them.
• Feel free to ask Dr. Brodie questions. He is a
very experienced researcher (unlike me…).
• After racing snakes we will return here for
further instruction.
Homework
• Write an ENTIRE lab report (Intro, Materials
and Methods, Results, Discussion). Don’t
forget a title!
• You should have AT LEAST 3 references. Two
primary sources and one secondary source.
• You have two weeks to do this assignment.
We will not have class the 24/25, 31/1. We
will meet again on November 7/8.
– Don’t wait until the last minute. I will read drafts,
but I’ll be in CA with a brand new niece and
travelling, so get them to me ASAP.
Suggestions
• Make sure you have hypotheses!!!! And,
make sure you have them for EVERY
experiment that you do within a lab!
• Answer the questions first, and then
incorporate them into the section that they fit
best.
• Write the results section after that. Every
section should relate back to your results. If it
doesn’t, then something needs to be adjusted.
Suggestions
• The subject put electrodes on their arm.
• The subject put electrodes on her arm.
• Don’t end sentences in prepositions!!!
• PROOFREAD!!!!!!!!