Authors: Claire Colvin ’27, Tess Everett ’27, Shiv Patel ’27. 

For our Neuroethology class (NSCI 324/BIOL 314) with Professor Charlotte Barkan, we decided to explore the extent to which TRPA1, an ion channel expressed by heat-sensing neurons, is involved in heat sensation. We wished to use optogenetics to investigate how the inactivation of cells expressing this channel influenced heat avoidance behaviors in Drosophila larvae. In order to inactivate the channel under blue light, we crossed two fly lines (UAS-ACR2 and GAL4-TRPA1) and used their resulting progeny. 

Students in Neuroethology 324 class collaborate with the Makerspace to create a dual-chamber water bath

To observe heat avoidance in ambient versus blue light, we wanted to create a model that could maintain a heat gradient with a cold and hot side of the arena (a Petri–dish). This led us to partner with the Makerspace to bring this experimental design to life. We helped design and then Makerspace student worker Izzie Tarantino ‘28 modeled and 3D printed a dual-chamber water bath that allowed us to cool and heat each side individually. The arena was partially submerged within the model, allowing for the creation of a temperature gradient to observe larval behavior. Heat avoidance behavior was quantified by recording the number of larvae present on each side of the arena at 30–second intervals over 5 minutes. We hypothesized that the inactivation of TRPA1 (blue light condition) would disrupt heat detection, manifesting as reduced heat avoidance of the hot side of the arena. 

Early data acquisition: small change in temperature

During our data collection, we learned that the temperature of the water did not exactly reflect the temperature of the arena. This was due to the material within the Petri-dish, called agar. While this substance is crucial because it facilitates larval movement, agar is not particularly conductive to heat. The cold side of the arena was warmer than the surrounding cold water beneath it, and the hot side of the arena was cooler than the surrounding hot water. This led us to adjust our methods. First, we opted for more extreme water temperatures within each chamber to achieve a true temperature gradient. We also decided to use an infrared thermometer to ensure we knew the exact temperature experienced by the larvae on the surface of the arena, instead of using the temperatures of the water below as a proxy. With these adjustments, we gathered much better data. 

Later data acquisition: larger change in temperature

Our preliminary results showed that the inactivation of TRPA1 partially leads to the reduction of heat avoidance behaviors, following our hypothesis that TRPA1 is involved in heat sensation, but demonstrating that TRPA1 is not the only ion channel involved in temperature detection. We would like to note that due to the few trials performed, these results are not statistically significant, and more experiments are required to confirm the viability of our findings. 

Special thanks to Jason Mativi (Senior Science Center Shop Engineer) and David Keiser-Clark (Makerspace Program Manager) for supporting our work.

For more in-depth information about our project and results, our final presentation and lab report are linked below:

• Final presentation: TRPA1 & Heat Avoidance: Ft. Drosophila Larvae (PDF, 16 slides)
• Lab report: Does Optogenetic Inactivation of TRPA1-expressing Neurons Diminish Heat Avoidance in Drosophila Larvae? (PDF, 7 pages)

Just us being goofy