Optogenetics in the teaching laboratory: using channelrhodopsin2 and Drosophila neurogenetics to teach principles of neuroethology
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1
Howard Hughes Medical Institute, Janelia Farms Research Institute, United States
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2
Cornell University, Neurobiology and Behavior, United States
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3
Cornell University, Psychology, United States
Optogenetic control of neuronal excitability is a powerful research tool to probe neural networks underlying behaviors. We are adapting recent advances in optogenetics and Drosophila neurogenetics for undergraduate teaching laboratories. Here we describe channelrhodopsin (ChR2) activation of specific neuronal populations to examine the neural basis of behavior in Drosophila larvae. Students use an inexpensive, easy to build light-emitting diode system for delivering blue light pulses with fine temporal control. They compare behavioral responses to blue light among wild-type larvae, larvae with ChR2 expressed in all sensory neurons and larvae with ChR2 expressed in class IV multi-dendritic (md IV) nociceptive neurons. Students observe and quantify larval behaviors evoked upon stimulation of sensory neurons in blue light in ChR2 expressing animals, and produce behavioral ethograms for the responses of each larval genotype. Behavioral observations are followed by intracellular recording of excitatory junctional potentials (EJPs) in larval muscles. In semi-intact preparations with the larval brain removed, students observe activation of EJPs by sensory stimulation with blue light. ChR2 activation of all peripheral sensory neurons triggers long lasting tonic bursts of EJPs. Activation of md IV neurons triggers bursts of EJPs and coordinated forward peristaltic waves in semi-intact preparations. When bursts of EJPs reflecting fictive crawling are seen in muscle fibers, students remotely activate sensory neurons and examine how sensory feedback at different phases of the rhythm reconfigures motor patterns. These experiments demonstrate reflex activation of motor patterns and reflex modulation of ongoing motor patterns underlying larval behavior. Students use state of the art research techniques and are provided with the tools to design and test their own novel research hypotheses. Feedback from students in a Cornell University neurophysiology class and from faculty participating in Cornell/ADInstruments and Faculty for Undergraduate Neuroscience sponsored teaching workshops demonstrates that these exercises increase student interest in genetics and neuroethology. Overall, these teaching modules provide a new platform for educators to teach principles of behavioral analysis and neural network operation, including central pattern generation and reflex control of motor networks.
Acknowledgements
Development of these exercises is supported by the American Physiological Society, Department of Neurobiology and Behavior at Cornell University and the Howard Hughes Medical Institute
Keywords:
central pattern generator,
channelrhodopsin2,
Drosophila,
Ethogram,
excitatory junctional potentials,
optogenetics,
Sensory reflex,
Teaching neuroethology
Conference:
Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012.
Presentation Type:
Poster Presentation (see alternatives below as well)
Topic:
Sensorimotor Integration
Citation:
Pulver
SR,
Menda
G,
Golden
JR and
Johnson
BR
(2012). Optogenetics in the teaching laboratory: using channelrhodopsin2 and Drosophila neurogenetics to teach principles of neuroethology.
Conference Abstract:
Tenth International Congress of Neuroethology.
doi: 10.3389/conf.fnbeh.2012.27.00399
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Received:
01 May 2012;
Published Online:
07 Jul 2012.
*
Correspondence:
Dr. Bruce R Johnson, Cornell University, Neurobiology and Behavior, Ithaca, NY, 14853, United States, brj1@cornell.edu