Name: determination of photoreceptor cell spectral sensitivity in an insect model from in vivo intracellular recordings
Uploaded: 2016-02-26T14:00:00.000+00:00
Duration: 8 min 33 s
Description: Watch this Scientific Journal Video about Determination of Photoreceptor Cell Spectral Sensitivity in an Insect Model from In Vivo Intracellular Recordings at JoVE.com

We thank the late&#160;Rudy Limburg for fabricating the cardan arm perimeter, Kimberly Jamison, Matthew McHenry, and Raju Metherate for lending us equipment, and Almut Kelber and Kentaro Arikawa, for encouragement. This work was supported by a National Science Foundation (NSF) Graduate Research Fellowship to KJM and NSF grant IOS-1257627 to A.D.B.

The authors declare that they have no competing financial interests.

Intracellular recording can be a difficult technique to master due to the many technical steps involved. For successful experiments several important points must be considered. First, it is important to have a properly vibrationally-isolated table on which the experiment is performed. Many researchers use air tables, which completely separate the tabletop from the base, giving superior vibration isolation. Our setup involves a thick marble table with a sandbox on top, into which is placed the micromanipulator/electrode h...

The electrical properties of cells such as neurons are observed by measuring ion flow across cell membranes as a change in voltage or current. A variety of electrophysiological techniques have been developed to measure bioelectric events in cells. Neurons found in the eyes of animals are accessible and their circuitry is often less complex than in the brain, making these cells good candidates for electrophysiological study. Common applications of electrophysiology in the eye include electroretinography (ERG)1,2 and microelectrode intracellular recording. ERG involves placing an electrode in or on the eye of an animal, applying a light stimulus, and measuring the change in voltage as a sum of the responses of all nearby cells3-6. If one is specifically interested in characterizing spectral sensitivities of individual photoreceptor cells, often multiple cell types simultaneously respond at different strengths&#160;to a given stimulus; thus it can be difficult to determine the sensitivities of specific cell types from ERG data especially if there are several different kinds of spectrally-similar photoreceptor cells in the eye. One potential solution is to create transgenic Drosophila with the photoreceptor (opsin) gene of interest expressed in the majority R1-6 cells in the eye and then perform ERGs7. Potential drawbacks of this method include no to low-expression of the photoreceptor protein8, and the long time frame for the generation and screening of transgenic animals. For eyes with fewer kinds of spectrally distinct photoreceptors, adaptation of the eye with colored filters can help with lowering the contribution of some cell types to the ERG, thereby permitting estimation of spectral sensitivity maxima9.
Intracellular recording is another technique where a fine electrode impales a cell and a stimulus is applied. The electrode records only that individual cell&#39;s response so that recording from and analyzing multiple individual cells can yield specific sensitivities of physiologically different cell types10-14. Although our protocol focuses on analysis of spectral sensitivity, the basic principles of intracellular recording with sharp electrodes are modifiable for other applications. Using a different preparation of a specimen, for instance, and using sharp quartz electrodes, one may record from deeper in the optic lobe or other regions in the brain, depending on the question being asked. For example, response times of individual photoreceptor cells15, cell activity in the optic lobes16 (lamina, medulla or lobula17), brain18 or other ganglia19 can also be recorded with similar techniques, or color stimuli could be replaced with polarization20-22 or motion stimuli23,24.
Phototransduction, the process by which light energy is absorbed and converted into an electrochemical signal, is an ancient trait common to nearly all present day animal phyla25. The visual pigment found in photoreceptor cells and responsible for initiating visual phototransduction is rhodopsin. Rhodopsins in all animals are made up of an opsin protein, a member of the 7 transmembrane G protein-coupled receptor family, and an associated chromophore which is derived from retinal or a similar molecule26,27. Opsin amino acid sequence and chromophore structure affect the absorbance of rhodopsin to different wavelengths of light. When a photon is absorbed by the chromophore the rhodopsin becomes activated, initiating a G-protein cascade in the cell that ultimately leads to the opening of membrane-bound ion channels28. Unlike most neurons, photoreceptor cells undergo graded potential changes that can be measured as a relative change in response amplitude with changing light stimulus. Typically a given photoreceptor type expresses only one opsin gene (though exceptions exist8,10,29-31). Sophisticated color vision, of the kind found in many vertebrates and arthropods, is achieved with a complex eye of hundreds or thousands of photoreceptor cells each expressing one or occasionally more rhodopsin types. Visual information is captured by comparing responses over the photoreceptor mosaic via complex downstream neural signaling in the eye and brain, resulting in the perception of an image complete with color and motion.
After measuring the raw responses of a photoreceptor cell to different wavelengths of light via intracellular recording, it is possible to calculate its spectral sensitivity. This calculation is based on the Principle of Univariance, which states that a photoreceptor cell&#39;s response is dependent on the number of photons it absorbs, but not on the particular properties of the photons it absorbs32. Any photon that is absorbed by rhodopsin will induce the same kind of response. In practice, this means that a cell&#39;s raw response amplitude will increase due to either an increase in light intensity (more photons to absorb), or to a shift in wavelength toward its peak sensitivity (higher probability of rhodopsin absorbing that wavelength). We make use of this principle in relating cellular responses at known intensity and the same wavelength to responses at different wavelengths and the same intensity but unknown relative sensitivity. Cell types are often identified by the wavelength at which their sensitivity peaks.
Here we show one method for intracellular recording and analysis of spectral sensitivity of photoreceptors in the eye of a butterfly, with a focus on making this method more accessible to the wider research community. Although intracellular recording remains common in the literature, particularly with respect to color vision in insects, we have found that descriptions of materials and methods are usually too brief to allow for reproduction of the technique. We present this method in video format with the aim of permitting its easier replication. We also describe the technique using easily obtainable and affordable equipment. We address common caveats that often are not reported, which slow down research when optimizing a new and complex technique.

<table><tbody><tr><td>Butterfly pupae</td><td></td><td></td><td>Several local species available, need USDA permits for shipping. Carolina Bio Supply has several insect species that may be ordered within the U.S. without the need for additional permits</td></tr><tr><td>Large plastic cylinder</td><td></td><td></td><td>Any chamber that remains humidified will work</td></tr><tr><td>Insect pins, size 2</td><td>BioQuip</td><td>1208B2</td><td></td></tr><tr><td>100% Desert Mesquite Honey</td><td>Trader Joe&#039;s</td><td></td><td>Any honey or sucrose solution will work</td></tr><tr><td>Xenon Arc Lamp</td><td>Oriel Instruments</td><td>66003</td><td>Oriel is now a part of Newport Corporation</td></tr><tr><td>Universal Power Supply</td><td>Oriel Instruments</td><td>68805</td><td>Oriel is now a part of Newport Corporation</td></tr><tr><td>Optical Track</td><td>Oriel Instruments</td><td>11190</td><td>Oriel is now a part of Newport Corporation</td></tr><tr><td>Rail Carrier, Large (2x)</td><td>Oriel Instruments</td><td>11641</td><td>Oriel is now a part of Newport Corporation</td></tr><tr><td>Rail Carrier, Small (4x)</td><td>Oriel Instruments</td><td>11647</td><td>Oriel is now a part of Newport Corporation</td></tr><tr><td>Thread Adaptor, 8-32 Male to 1/4-20 Male, pack of 10</td><td>Newport Corporation</td><td>TA-8Q20-10</td><td></td></tr><tr><td>Optical Mounting Post, 1.0 in., 0.5 in. Dia. Stainless, 8-32 &amp;amp; 1/4-20 (5x)</td><td>Newport Corporation</td><td>SP-1</td><td></td></tr><tr><td>No Slip Optical Post Holder, 2 in., 0.5 in. Diameter Posts, 1/4-20 (5x)</td><td>Newport Corporation</td><td>VPH-2</td><td></td></tr><tr><td>Fixed lens mount, 50.8 mm</td><td>Newport Corporation</td><td>LH-2</td><td></td></tr><tr><td>Fixed lens mount, 25.4 mm</td><td>Newport Corporation</td><td>LH-1</td><td></td></tr><tr><td>Condenser lens assembly</td><td>Newport Corporation</td><td>60006</td><td></td></tr><tr><td>Convex silica lens, 50.8 mm</td><td>Newport Corporation</td><td>SPX055</td><td></td></tr><tr><td>Six Position Filter Wheel, x2</td><td>Newport Corporation</td><td>FW1X6</td><td></td></tr><tr><td>Filter Wheel Mount Hub</td><td>Newport Corporation</td><td>FWM</td><td></td></tr><tr><td>Concave silica lens, 25.4 mm</td><td>Newport Corporation</td><td>SPC034</td><td></td></tr><tr><td>Collimator holder</td><td>Newport Corporation</td><td>77612</td><td></td></tr><tr><td>Collimating beam probe</td><td>Newport Corporation</td><td>77644</td><td></td></tr><tr><td>Ferrule Converter, SMA Termination to 11 mm Standard Ferrule</td><td>Newport Corporation</td><td>77670</td><td>This adapter allows the fiber optic to fit into the collimator holder&amp;nbsp;</td></tr><tr><td>600 &amp;mu;m diameter UV-vis fiber obtic cable</td><td>Oriel Instruments</td><td>78367</td><td>Oriel is now a part of Newport Corporation</td></tr><tr><td>Shutter with drive unit</td><td>Uniblitz</td><td>100-2B</td><td></td></tr><tr><td>UV Fused Silica Metallic ND Filter, 0.1 OD</td><td>Newport</td><td>FRQ-ND01</td><td></td></tr><tr><td>UV Fused Silica Metallic ND Filter, 0.3 OD</td><td>Newport</td><td>FRQ-ND03</td><td></td></tr><tr><td>UV Fused Silica Metallic ND Filter, 0.5 OD</td><td>Newport</td><td>FRQ-ND05</td><td></td></tr><tr><td>UV Fused Silica Metallic ND Filter, 1.0 OD</td><td>Newport</td><td>FRQ-ND10</td><td></td></tr><tr><td>UV Fused Silica Metallic ND Filter, 2.0 OD</td><td>Newport</td><td>FRQ-ND30</td><td></td></tr><tr><td>UV Fused Silica Metallic ND Filter, 3.0 OD</td><td>Newport</td><td>FRQ-ND50</td><td></td></tr><tr><td>LS-1-Cal lamp</td><td>Ocean Optics</td><td>LS-1-Cal</td><td></td></tr><tr><td>Spectrometer</td><td>Ocean Optics</td><td>USB-2000</td><td></td></tr><tr><td>SpectraSuite Software</td><td>Ocean Optics</td><td></td><td></td></tr><tr><td>Interference bandpass filter, 300 nm&amp;nbsp;</td><td>Edmund Optics</td><td>67749</td><td></td></tr><tr><td>Interference bandpass filter, 310 nm&amp;nbsp;</td><td>Edmund Optics</td><td>67752</td><td></td></tr><tr><td>Interference bandpass filter, 320 nm&amp;nbsp;</td><td>Edmund Optics</td><td>67754</td><td></td></tr><tr><td>Interference bandpass filter, 330 nm&amp;nbsp;</td><td>Edmund Optics</td><td>67756</td><td></td></tr><tr><td>Interference bandpass filter, 340 nm&amp;nbsp;</td><td>Edmund Optics</td><td>65614</td><td></td></tr><tr><td>Interference bandpass filter, 350 nm&amp;nbsp;</td><td>Edmund Optics</td><td>67757</td><td></td></tr><tr><td>Interference bandpass filter, 360 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6X, 12X, 25X, 50X magnification</td><td>Wild Heerbrugg</td><td>Wild M5</td><td>Any Stereomicroscope will do</td></tr><tr><td>Microscope stand with swinging arm and heavy base</td><td>McBain Instruments</td><td></td><td>Any heavy base with arm will do</td></tr><tr><td>Cardan arm</td><td></td><td></td><td>Custom built, See &lt;strong&gt;Figure 4&lt;/strong&gt;</td></tr><tr><td>Fiber-lite high intensity illuminator</td><td>Dolan-Jenner</td><td>MI-150</td><td>For lighting specimen</td></tr><tr><td>Fiber-lite goose-neck light guide</td><td>Dolan-Jenner</td><td>EEG 2823</td><td>Any goose-neck light guide will do</td></tr><tr><td>Marble table</td><td></td><td></td><td></td></tr><tr><td>Raised wooden table</td><td></td><td></td><td>Hole should be cut through this table so that the sandbox can rest on the marble table underneath</td></tr><tr><td>Wooden box filled with sand</td><td></td><td></td><td>custom built, any box with sand</td></tr><tr><td>Manipulator</td><td>Carl Zeiss - Jena</td><td></td><td></td></tr><tr><td>Electrode holder</td><td></td><td></td><td></td></tr><tr><td>Specimen stage</td><td></td><td></td><td></td></tr><tr><td>Alligator clip wires for grounding</td><td></td><td></td><td></td></tr><tr><td>Insulated copper wire</td><td></td><td></td><td></td></tr><tr><td>Silver wire, 0.125 mm diameter</td><td>World Precision Instruments</td><td>AGW0510</td><td></td></tr><tr><td>BNC cables</td><td></td><td></td><td></td></tr><tr><td>Preamplifier with headstage</td><td>Dagan Corporation</td><td>IX2-700</td><td></td></tr><tr><td>Humbug Noise reducer</td><td>Quest Scientific</td><td>Humbug</td><td></td></tr><tr><td>Oscilloscope, 30 MHz, 2 CH, Dual Trace, Alt-triggering, without probe</td><td>EZ Digital</td><td>os-5030</td><td></td></tr><tr><td>BNC T-adapter</td><td></td><td></td><td></td></tr><tr><td>Powerlab hardware 2/20</td><td>ADI instruments</td><td>ML820</td><td></td></tr><tr><td>Labchart software</td><td>ADI instruments</td><td>Chart 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determination of photoreceptor cell spectral sensitivity in an insect model from in vivo intracellular recordings

Intracellular recording is a powerful technique used to determine how a single cell may respond to a given stimulus. In vision research, intracellular recording has historically been a common technique used to study sensitivities of individual photoreceptor cells to different light stimuli that is still being used today. However, there remains a dearth of detailed methodology in the literature for researchers wishing to replicate intracellular recording experiments in the eye. Here we present the insect as a model for examining eye physiology more generally. Insect photoreceptor cells are located near the surface of the eye and are therefore easy to reach, and many of the mechanisms involved in vision are conserved across animal phyla. We describe the basic procedure for in vivo intracellular recording of photoreceptor cells in the eye of a butterfly, with the goal of making this technique more accessible to researchers with little prior experience in electrophysiology. We introduce the basic equipment needed, how to prepare a live butterfly for recording, how to insert a glass microelectrode into a single cell, and finally the recording procedure itself. We also explain the basic analysis of raw response data for determining spectral sensitivity of individual cell types. Although our protocol focuses on determining spectral sensitivity, other stimuli (e.g., polarized light) and variations of the method are applicable to this setup.

For many elements of the recording setup, a written description does not provide enough detail. Figure 1 is a schematic of the components involved in the complete recording setup. In Figure 2, spectra are plotted for white light and each interference filter to give a sense of why a correction factor is needed and what is needed to calculate this correction. Figure 3 shows photos and a diagram of the Cardan arm that is used for these experiments. Figure 4...

Watch this Scientific Journal Video about Determination of Photoreceptor Cell Spectral Sensitivity in an Insect Model from In Vivo Intracellular Recordings at JoVE.com

Determination of Photoreceptor Cell Spectral Sensitivity in an Insect Model from In Vivo Intracellular Recordings

The electrophysiological technique of intracellular recording is demonstrated and used to determine spectral sensitivities of single photoreceptor cells in the compound eye of a butterfly.

Determination of Photoreceptor Cell Spectral Sensitivity in an Insect Model from In Vivo Intracellular Recordings

Intracellular recording is a powerful technique used to determine how a single cell may respond to a given stimulus. In vision research, intracellular ...

determination-photoreceptor-cell-spectral-sensitivity-an-insect-model

Research

JoVE Journal

Neuroscience

11.4K Views.  University of California, Irvine. The electrophysiological technique of intracellular recording is demonstrated and used to determine spectral sensitivities of single photoreceptor cells in the compound eye of a butterfly.

Video: Determination of Photoreceptor Cell Spectral Sensitivity in an Insect Model from In Vivo Intracellular Recordings

Dissection and Culture of Commissural Neurons from Embryonic Spinal Cord

Commissural neurons have been widely used to investigate the mechanisms underlying axon guidance during embryonic spinal cord development. The cell bodies of these neurons are located in the dorsal spinal cord and their axons follow stereotyped trajectories during embryonic development. Commissural axons initially project ventrally towards the floorplate. After crossing the midline, these axons turn anteriorly and project towards the brain. Each of these steps is regulated by the action of several guidance cues. Cultures highly enriched in commissural neurons are ideally suited for many experiments addressing the mechanisms of axon pathfinding, including turning assays, immunochemistry and biochemistry. Here, we describe a method to dissect and culture commissural neurons from E13 rat dorsal spinal cord. First, the spinal cord is isolated and dorsal strips are dissected out. The dorsal tissue is then dissociated into a cell suspension by trypsinization and mechanical disruption. Neurons are plated onto poly-L-lysine-coated glass coverslips or tissue-culture dishes. After 30 hours in vitro, most neurons have extended an axon. The purity of the culture (Yam et al. 2009), typically over 90%, can be assessed by immunolabeling with the commissural neuron markers DCC, LH2 and TAG1 (Helms and Johnson, 1998). This neuronal preparation is a useful tool for in vitro studies of the cellular and molecular mechanisms of commissural axon growth and guidance during spinal cord development.

This video demonstrates a method to dissect and culture commissural neurons from E13 rat dorsal spinal cord. Dissociated commissural neurons are useful to study the cellular and molecular mechanisms of axon growth and guidance.

Commissural neurons have been widely used to investigate the mechanisms underlying axon guidance during embryonic spinal cord development. The cell bodies ...

Single-unit In vivo Recordings from the Optic Chiasm of Rat

Information about the visual world is transmitted to the brain in sequences of action potentials in retinal ganglion cell axons that make up the optic nerve. In vivo recordings of ganglion cell spike trains in several animal models have revealed much of what is known about how the early visual system processes and encodes visual information. However, such recordings have been rare in one of the most common animal models, the rat, possibly owing to difficulty in detecting spikes fired by small diameter axons. The many retinal disease models involving rats motivate a need for characterizing the functional properties of ganglion cells without disturbing the eye, as with intraocular or in vitro recordings. Here, we demonstrate a method for recording ganglion cell spike trains from the optic chiasm of the anesthetized rat. We first show how to fabricate tungsten-in-glass electrodes that can pick up electrical activity from single ganglion cell axons in rat. The electrodes outperform all commercial ones that we have tried. We then illustrate our custom-designed stereotaxic system for in vivo visual neurophysiology experiments and our procedures for animal preparation and reliable and stable electrode placement in the optic chiasm.

Single-unit In vivo Recordings from the Optic Chiasm of Rat

Retinal ganglion cells transmit visual information from the eye to the brain with sequences of action potentials. Here, we demonstrate how to record the action potentials of single ganglion cells in vivo from anesthetized rats.

Information about the visual world is transmitted to the brain in sequences of action potentials in retinal ganglion cell axons that make up the optic ...

Electrophysiological Characterization of GFP-Expressing Cell Populations in the Intact Retina

Studying the physiological properties and synaptic connections of specific neurons in the intact tissue is a challenge for those cells that lack conspicuous morphological features or show a low population density. This applies particularly to retinal amacrine cells, an exceptionally multiform class of interneurons that comprise roughly 30 subtypes in mammals1. Though being a crucial part of the visual processing by shaping the retinal output2, most of these subtypes have not been studied up to now in a functional context because encountering these cells with a recording electrode is a rare event.
Recently, a multitude of transgenic mouse lines is available that express fluorescent markers like green fluorescent protein (GFP) under the control of promoters for membrane receptors or enzymes that are specific to only a subset of neurons in a given tissue3,4. These pre-labeled cells are therefore accessible to directed microelectrode targeting under microscopic control, permitting the systematic study of their physiological properties in situ. However, excitation of fluorescent markers is accompanied by the risk of phototoxicity for the living tissue. In the retina, this approach is additionally hampered by the problem that excitation light causes appropriate stimulation of the photoreceptors, thus inflicting photopigment bleaching and transferring the retinal circuits into a light-adapted condition. These drawbacks are overcome by using infrared excitation delivered by a mode-locked laser in short pulses of the femtosecond range. Two-photon excitation provides energy sufficient for fluorophore excitation and at the same time restricts the excitation to a small tissue volume minimizing the hazards of photodamage5. Also, it leaves the retina responsive to visual stimuli since infrared light (&gt;850 nm) is only poorly absorbed by photopigments6.
In this article we demonstrate the use of a transgenic mouse retina to attain electrophysiological in situ recordings from GFP-expressing cells that are visually targeted by two-photon excitation. The retina is prepared and maintained in darkness and can be subjected to optical stimuli which are projected through the condenser of the microscope (Figure 1). Patch-clamp recording of light responses can be combined with dye filling to reveal the morphology and to check for gap junction-mediated dye coupling to neighboring cells, so that the target cell can by studied on different experimental levels.

This article depicts the recording of individual cells from fluorescently tagged neuronal populations in the intact mouse retina. By using two-photon infrared excitation transgenetically labeled cells were targeted for patch-clamp recording to study their light responses, receptive field properties, and morphology.

Studying the physiological properties and synaptic connections of specific neurons in the intact tissue is a challenge for those cells that lack ...

Retrograde Fluorescent Labeling Allows for Targeted Extracellular Single-unit Recording from Identified Neurons In vivo

The overall goal of this method is to record single-unit responses from an identified population of neurons. In vivo electrophysiological recordings from individual neurons are critical for understanding how neural circuits function under natural conditions. Traditionally, these recordings have been performed 'blind', meaning the identity of the recorded cell is unknown at the start of the recording. Cellular identity can be subsequently determined via intracellular1, juxtacellular2 or loose-patch3 iontophoresis of dye, but these recordings cannot be pre-targeted to specific neurons in regions with functionally heterogeneous cell types. Fluorescent proteins can be expressed in a cell-type specific manner permitting visually-guided single-cell electrophysiology4-6. However, there are many model systems for which these genetic tools are not available. Even in genetically accessible model systems, the desired promoter may be unknown or genetically homogenous neurons may have varying projection patterns. Similarly, viral vectors have been used to label specific subgroups of projection neurons7, but use of this method is limited by toxicity and lack of trans-synaptic specificity. Thus, additional techniques that offer specific pre-visualization to record from identified single neurons in vivo are needed. Pre-visualization of the target neuron is particularly useful for challenging recording conditions, for which classical single-cell recordings are often prohibitively difficult8-11. The novel technique described in this paper uses retrograde transport of a fluorescent dye applied using tungsten needles to rapidly and selectively label a specific subset of cells within a particular brain region based on their unique axonal projections, thereby providing a visual cue to obtain targeted electrophysiological recordings from identified neurons in an intact circuit within a vertebrate CNS.
The most significant novel advancement of our method is the use of fluorescent labeling to target specific cell types in a non-genetically accessible model system. Weakly electric fish are an excellent model system for studying neural circuits in awake, behaving animals12. We utilized this technique to study sensory processing by "small cells" in the anterior exterolateral nucleus (ELa) of weakly electric mormyrid fish. "Small cells" are hypothesized to be time comparator neurons important for detecting submillisecond differences in the arrival times of presynaptic spikes13. However, anatomical features such as dense myelin, engulfing synapses, and small cell bodies have made it extremely difficult to record from these cells using traditional methods11, 14. Here we demonstrate that our novel method selectively labels these cells in 28% of preparations, allowing for reliable, robust recordings and characterization of responses to electrosensory stimulation.

Retrograde Fluorescent Labeling Allows for Targeted Extracellular Single-unit Recording from Identified Neurons In vivo

Retrograde transport of fluorescent dye labels a sub-population of neurons based on anatomical projection. Labeled axons can be visually targeted in vivo, permitting extracellular recording from identified axons. This technique facilitates recording when neurons cannot be labeled through genetic manipulation or are difficult to isolate using 'blind' in vivo approaches.

The overall goal of this method is to record single-unit responses from an identified population of neurons. In vivo electrophysiological recordings from ...

Electrophysiological Method for Recording Intracellular Voltage Responses of Drosophila Photoreceptors and Interneurons to Light Stimuli In Vivo

Voltage responses of insect photoreceptors and visual interneurons can be accurately recorded with conventional sharp microelectrodes. The method described here enables the investigator to measure long-lasting (from minutes to hours) high-quality intracellular responses from single Drosophila R1-R6 photoreceptors and Large Monopolar Cells (LMCs) to light stimuli. Because the recording system has low noise, it can be used to study variability among individual cells in the fly eye, and how their outputs reflect the physical properties of the visual environment. We outline all key steps in performing this technique. The basic steps in constructing an appropriate electrophysiology set-up for recording, such as design and selection of the experimental equipment are described. We also explain how to prepare for recording by making appropriate (sharp) recording and (blunt) reference electrodes. Details are given on how to fix an intact fly in a bespoke fly-holder, prepare a small window in its eye and insert a recording electrode through this hole with minimal damage. We explain how to localize the center of a cell's receptive field, dark- or light-adapt the studied cell, and to record its voltage responses to dynamic light stimuli. Finally, we describe the criteria for stable normal recordings, show characteristic high-quality voltage responses of individual cells to different light stimuli, and briefly define how to quantify their signaling performance. Many aspects of the method are technically challenging and require practice and patience to master. But once learned and optimized for the investigator's experimental objectives, it grants outstanding in vivo neurophysiological data.

Electrophysiological Method for Recording Intracellular Voltage Responses of Drosophila Photoreceptors and Interneurons to Light Stimuli In Vivo

Sharp microelectrodes enable accurate electrophysiological characterization of photoreceptor and visual interneuron output in living Drosophila. Here we show how to use this method to record high-quality voltage responses of individual cells to controlled light stimulation. This method is ideal for studying neural information processing in insect compound eyes.

Voltage responses of insect photoreceptors and visual interneurons can be accurately recorded with conventional sharp microelectrodes. The method ...

Electrophysiological Method for Whole-cell Voltage Clamp Recordings from Drosophila Photoreceptors

Whole-cell voltage clamp recordings from Drosophila melanogaster photoreceptors have revolutionized the field of invertebrate visual transduction, enabling the use of D. melanogaster molecular genetics to study inositol-lipid signaling and Transient Receptor Potential (TRP) channels at the single-molecule level. A handful of labs have mastered this powerful technique, which enables the analysis of the physiological responses to light under highly controlled conditions. This technique allows control over the intracellular and extracellular media; the membrane voltage; and the fast application of pharmacological compounds, such as a variety of ionic or pH indicators, to the intra- and extracellular media. With an exceptionally high signal-to-noise ratio, this method enables the measurement of dark spontaneous and light-induced unitary currents (i.e.&#160;spontaneous and quantum bumps) and macroscopic Light-induced Currents (LIC) from single D. melanogaster photoreceptors. This protocol outlines, in great detail, all the key steps necessary to perform this technique, which includes both electrophysiological and optical recordings. The fly retina dissection procedure for the attainment of intact and viable ex vivo isolated ommatidia in the bath chamber is described. The equipment needed to perform whole-cell and fluorescence imaging measurements are also detailed. Finally, the pitfalls in using this delicate preparation during extended experiments are explained.

Electrophysiological Method for Whole-cell Voltage Clamp Recordings from Drosophila Photoreceptors

Whole-cell recordings from Drosophila melanogaster photoreceptors enable the measurement of spontaneous dark bumps, quantum bumps, macroscopic responses to light, and current-voltage relationships under various conditions. In combination with D. melanogaster genetic manipulation tools, this method enables the study of the ubiquitous inositol-lipid signaling pathway and its target, the TRP channel.

Whole-cell voltage clamp recordings from Drosophila melanogaster photoreceptors have revolutionized the field of invertebrate visual transduction, ...

Desensitization and Recovery of Crayfish Photoreceptors Upon Delivery of a Light Stimulus

A method to study desensitization and recovery of crayfish photoreceptors is presented. We performed intracellular electrical recordings of photoreceptor cells in isolated eyestalks using the discontinuous single electrode-switched voltage-clamp configuration. First, with a razor blade we made an opening in the dorsal cornea to get access to the retina. Thereafter, we inserted a glass electrode through the opening, and penetrated a cell as reported by the recording of a negative potential. Membrane potential was clamped at the photoreceptor's resting potential and a light-pulse was applied to activate currents. Finally, the two light-flash protocol was employed to measure current desensitization and recovery. The first light-flash triggers, after a lag period, the transduction ionic current, which after reaching a peak amplitude decays towards a desensitized state; the second flash, applied at varying time intervals, assesses the state of the light-activated conductance. To characterize the light-elicited current, three parameters were measured: 1) latency (the time elapsed between light flash delivery and the moment in which current achieves 10% of its maximum value); 2) peak current; and 3) desensitization time constant (exponential time constant of the current decay phase). All parameters are affected by the first pulse.
To quantify recovery from desensitization, the ratio p2/p1 was employed versus time between pulses. p1 is the peak current evoked by the first light-pulse, and p2 is the peak current evoked by the second pulse. These data were fitted to a sum of exponential functions. Finally, these measurements were carried out as function of circadian time.

A protocol for the study of desensitization and sensitivity recovery of crayfish photoreceptors as a function of circadian time is presented.

A method to study desensitization and recovery of crayfish photoreceptors is presented. We performed intracellular electrical recordings of photoreceptor ...

Electrophysiological Methods for Measuring Photopigment Levels in Drosophila Photoreceptors

The Drosophila G-protein-coupled photopigment rhodopsin (R) is composed of a protein (opsin) and a chromophore. The activation process of rhodopsin is initiated by photon absorption-inducing isomerization of the chromophore, promoting conformational changes of the opsin and resulting in a second dark-stable photopigment state (metarhodopsin, M). Investigation of this bi-stable photopigment using random mutagenesis requires simple and robust methods for screening mutant flies. Therefore, several methods for measuring reductions in functional photopigment levels have been designed. One such method exploits the charge displacements within the photopigment following photon absorption and the huge amounts of photopigment molecules expressed in the photoreceptors. This electrical signal, named the early receptor potential (or early receptor current), is measured by a variety of electrophysiological methods (e.g., electroretinogram and whole-cell recordings) and is linearly proportional to functional photopigment levels. The advantages of this method are the high signal-to-noise ratio, direct linear measurement of photopigment levels, and independence of phototransduction mechanisms downstream to rhodopsin or metarhodopsin activation. An additional electrophysiological method called prolonged depolarizing afterpotential (PDA) exploits the bi-stability of Drosophila photopigment and the absorption-spectral differences of fly R and M pigment states. The PDA is induced by intense blue light, converting saturating amounts of rhodopsin to metarhodopsin, resulting in the failure of light-response termination for an extended time in darkness, but it can be terminated by metarhodopsin to rhodopsin conversion using intense orange light. Since the PDA is a robust signal that requires massive photopigment conversion, even small defects in the biogenesis of the photopigment lead to readily detected abnormal PDA. Indeed, defective PDA mutants led to the identification of novel signaling proteins important for phototransduction.

Electrophysiological Methods for Measuring Photopigment Levels in Drosophila Photoreceptors

We present a protocol to electrophysiologically characterize bi-stable photopigments: (i) exploiting the charge displacements within the photopigment molecules following photon-absorption and their huge amount in the photoreceptors, and (ii) exploiting the absorption-spectra differences of rhodopsin and metarhodopsin photopigment states. These protocols are useful to screen for mutations affecting bi-stable photopigment systems.&#160;

The Drosophila G-protein-coupled photopigment rhodopsin (R) is composed of a protein (opsin) and a chromophore. The activation process of rhodopsin is ...

In Vivo Intracellular Recording of Photoreceptor Cell Spectral Sensitivity in a Butterfly

Source: McCulloch, K. J., et al.. <a href="https://app.jove.com/v/53829">Determination of Photoreceptor Cell Spectral Sensitivity in an Insect Model from In Vivo Intracellular Recordings.</a> J. Vis. Exp. (2016)
This video demonstrates the procedure for in vivo intracellular recording of photoreceptor cells in the eye of a butterfly and determining the spectral sensitivity of individual cell types. This technique enables the study of sensitivities of individual photoreceptor cells to different light stimuli.

1. Specimen Prep and Recording Procedure

	Prepare the Specimen
	
		Affix an individual butterfly inside a small plastic tube with hot wax so the head is ...

JoVE Encyclopedia of Experiments

Neurophysiology

Imaging and Optical Techniques

Electrophysiological Recording of Voltage Responses of Drosophila Retinal Photoreceptors to Light Stimuli

Source: Juusola, M., et al. <a href="https://app.jove.com/v/54142">Electrophysiological Method for Recording Intracellular Voltage Responses of Drosophila Photoreceptors and Interneurons to Light Stimuli In Vivo.</a> J. Vis. Exp. (2016).
This video outlines the protocol for electrophysiological recording of photoreceptor activity in the eye of an immobilized Drosophila, enabling precise measurement of voltage changes in response to light stimuli.

1. Recording from R1-R6 Photoreceptors 

	Always be grounded when operating the microelectrode amplifier (for example by touching the metal surface of the ...

Determination of Photoreceptor Cell Spectral Sensitivity in an Insect Model from In Vivo Intracellular Recordings

Summary

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Chapters in this video

Dissection and Culture of Commissural Neurons from Embryonic Spinal Cord

Single-unit In vivo Recordings from the Optic Chiasm of Rat

Electrophysiological Characterization of GFP-Expressing Cell Populations in the Intact Retina

Retrograde Fluorescent Labeling Allows for Targeted Extracellular Single-unit Recording from Identified Neurons In vivo

Electrophysiological Method for Recording Intracellular Voltage Responses of Drosophila Photoreceptors and Interneurons to Light Stimuli In Vivo

Electrophysiological Method for Whole-cell Voltage Clamp Recordings from Drosophila Photoreceptors

Desensitization and Recovery of Crayfish Photoreceptors Upon Delivery of a Light Stimulus

Electrophysiological Methods for Measuring Photopigment Levels in Drosophila Photoreceptors

In Vivo Intracellular Recording of Photoreceptor Cell Spectral Sensitivity in a Butterfly

Electrophysiological Recording of Voltage Responses of Drosophila Retinal Photoreceptors to Light Stimuli