Tetrodotoxin. Tetrodotoxin (TTX) Low molecular weight neurotoxin. Blocks pore region of voltage-gated sodium channels. Prevents propagation of action.

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!!!!!!!!