Optogenetic Control of Fly Optomotor Responses.

Väinö Haikala, Maximilian Joesch, Alexander Borst, and Alex S. Mauss.
J Neurosci. 2013 Aug 21;33(34):13927-34. PMID: 23966712

 

Objective:   Drosophila rely on visual stimulation in order to control their navigation, as has been shown by head movements and flight-turning in response to rotating visual patterns.  The horizontal optomotor response has been thought to rely on three neurons known as the horizontal system (HS) cells, a subset of the lobula plate tangential cells (LPTCs).  Here, a bistable channelrhodopsin was used in order to demonstrate the role of the HS in optomotor control.

Methods:    R27B03-Gal4 flies were crossed with transgenic pUASt-ChR2-C128S-eYFP flies in order to restrict ChR2 expression to HS cells.  For elctrophysiological experiments, HS cells were exposed and used for whole cell recording.  For behavioral experiments, flies were tethered and changes in head and wing movement were measured under infrared light.  472nm and 565nm light was delivered to the HCs by optical fiber at 10mW and 6mW, respectively.  Preferential expression in HS cells was verified by confocal microscopy.

Results:

·         In phototransduction-mutant blind flies, optogenetic stimulation resulted in depolarization of HS neurons similar to that seen in wild type flies under visual stimulation.  When ChR was expressed in normal flies, optogenetic stimulation caused a similar response, even while the flies were being given other visual stimuli.

·         Flies expressing ChR showed significantly greater head turning in response to optogenetic stimulation when compared to wild type flies.  This change was even greater in the blind flies.

·         When tethered flies were examined for changes in wing movement / flight-turning, ChR expressing flies showed significant yaw when compared to wild type flies.  Again, this response was even greater in blind flies.

-DH