We’re excited to share the first of three recent research papers featuring our very own CoolLED pE-800 Illumination System.
This month, you can learn about the role of optogenetics to understand emergency SatNav in mice!
How Emergency ‘Bio-SatNav’ Works
Survival favours the fittest, but also favours those individuals that can make the fastest escape to shelter. A mouse can’t always outrun a predator, but is more likely to survive if it can quickly recall and locate its nearest hiding place.
But how exactly does it process the positional and navigational information necessary for the speediest life-saving escape?
This was the question asked by researchers Dr Dario Campagner and collaborators, whose study has been published in Nature.1
The authors studied how mice responded to threatening sounds, and focused on analysing two specific regions of the brain: the Retrosplenial cortex (RSP) and Superior colliculus (SC) which are involved in taking in spatial information, processing it and generating a response.
Firstly, they analysed neuronal firing patterns in these regions while mice were investigating their surroundings, and when seeking shelter. Next, they inactivated these areas to indicate their significance. One particularly interesting finding was that inactivating the RSP-SC pathway only impacted the ability to find shelter. It had no impact on navigating towards a reward, indicating its distinct role in escape scenarios.
The next part of the study picked apart the pathway’s neuronal mechanisms. Following in vivo experiments to build up an overall picture of the RSP-SC circuit structure, the authors turned to in vitro analysis for a more detailed understanding of the connections between the RSP and SC. Optogenetics presents a useful tool for analysing such neuronal interactions, and this approach helped prove the existence of the RSP-SC circuit structure based on feedforward lateral inhibition.
In a sophisticated dual-opsin approach, Channelrhodopsin-2 (ChrR2) was expressed only in SC inhibitory neurons receiving input from the RSP. The opsin ChrimsonR was also expressed in the RSP.
Firstly, excitatory SC cells were identified by tagging with Gcamp7f, and located with widefield fluorescence using the 470 nm LED of the pE-800, and whole-cell patch clamp electrophysiology recordings were made. ChrimsonR was then activated using the 635 nm LED, which identified any of those tagged excitatory SC cells receiving input from the RSP. By also activating ChR2 with the 435 nm LED, inhibition could then be analysed within the circuit.
This confirmed the existence of the feedforward lateral inhibition circuit involving excitatory and inhibitory neurons. The authors have therefore successfully uncovered a mechanism whereby mice continuously monitor surroundings and calculate the best escape route using their emergency ‘Bio-Sat-Nav’.
About the pE-800
The CoolLED pE-800 includes eight LED channels covering the major fluorophores and opsins.
The ability to have any combination of these switched on and control the intensity allows multiple fluorophores to be excited in parallel, while high-speed TTL triggering and synchronisation enables accurate and precise control of complex pulsing protocols.
This is particularly useful for neuroscience applications.
CoolLED specialises in LED microscope lighting and, since our team of four introduced the first commercially available LED microscope illuminator in 2006, we have led the way in designing and manufacturing cutting edge LED Illuminators for Microscopes using the latest technology.