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!!!!!!!!