This study was supported by MEXT-Supported Program for the Strategic Research Foundation at Private Universities and JSPS Young Scientist B grant for H.T. We would like to thank Ohtake Norihito to edit the video clips.

1. Prepare apple plate
<ol>
	<li>Mix 12.5 g agar, 125 ml 100% commercially available apple juice, 12.5 g glucose, and 375 ml H2O. Microwave the mixture for 1 to 2 minutes and pour to the 3 cm cell culture dish. Store at 4 &#176;C.</li>
</ol>
2. Genetic cross
<ol>
	<li>Use the following representative genetic cross:</li>
</ol>
Or49a-mCD8::GFP/CyO x w1118
3. Dissection and staining protocol
<ol>
	<li>Anesthetize the fly and then cut the fly head vertically by holding it using a forceps.</li>
	<li>Carefully place the antennae containing portion on an apple plate.</li>
	<li>Cut the third segment of the antenna using fine dissection scissors.</li>
	<li>Place 90 &#181;l of the fixation solution (4% paraformaldehyde in 0.1% PBST (PBS with 0.1% Triton X-100)) to the middle of a glass bottom culture dish.</li>
	<li>Gently transfer the dissected antennae with a sharp needle directly to the fixation solution. If necessary, physically submerge the antennae into the solution using needle.</li>
	<li>Incubate for 40 minutes at room temperature (RT). Wash the antennae in 0.4% PBST (PBS with 0.4% Triton X-100), 3x 10 minutes in each, keeping them in the same dish. Use yellow tips to remove and add PBST solution. Use 90 &#181;l of the wash solution each time. 
	NOTE: Do not place the dish into a shaker during immunohistochemistry. Before removing or adding the solution into the dish, bring all the antennae into the center of the dish using the needle and carefully add or remove the solution from the edge of the dish.</li>
	<li>Block the antennae with 90 &#181;l of 5% normal horse serum in 0.1% PBST for 20 minutes at RT.</li>
	<li>After removing the blocking solution, incubate the antennae with 90&#181;l of primary antibodies in 0.1% PBST containing 5% horse serum for 48 hr at 4 &#176;C in a moistened container as described previously8.</li>
	<li>Wash the antennae 6x 10 minutes in 0.4% PBST.</li>
	<li>Incubate the antennae with 90 &#181;l of secondary antibodies in 0.1% PBST containing 5% horse serum for 48 hr at 4 &#176;C. Wash 6x 10 minutes using 0.4% PBST.</li>
	<li>To mount the antennae, remove PBST from the culture dish as much as possible and gradually introduce two different concentrations of glycerol to the antennae. First add 40% glycerol to the dish for 1 to 2 minutes; then remove this and add 80% glycerol.</li>
	<li>Carefully extract the antennae (including 80% glycerol) from the culture dish using yellow tip and place them onto a slide. Gently place a coverslip on top and seal the coverslip edges with nail polish. The antennae are now ready to be imaged by fluorescence microscopy.</li>
</ol>

<ol>
	<li>Christensen, T. A., White, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Representation of olfactory information in the brain In The Neurobiology of Taste and Smell. , 201-232 (2000).</li><li>Ache, B. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Towards+a+common+strategy+for+transducing+olfactory+information.">Towards a common strategy for transducing olfactory information.</a> Sem. Cell Biol. 5, 55-63 (1994).</li><li>Bargmann, C. I., Hartwieg, E., Horvitz, H. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Odorant-selective+genes+and+neurons+mediate+olfaction.">Odorant-selective genes and neurons mediate olfaction.</a> C. elegans. Cell. 13, 515-527 (1993).</li><li>Barth, A. L., Justice, N. J., Ngai, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Asynchronous+onset+of+odorant+receptor+expression+in+the+developing+zebrafish+olfactory+system.">Asynchronous onset of odorant receptor expression in the developing zebrafish olfactory system.</a> Neuron. 16, 23-34 (1996).</li><li>Firestein, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=How+the+olfactory+system+makes+sense+of+scents.">How the olfactory system makes sense of scents.</a> Nature. 413, 211-218 (2001).</li><li>Stockinger, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neural+circuitry+that+governs+Drosophila+male+courtship+behavior.">Neural circuitry that governs Drosophila male courtship behavior.</a> Cell. 121, 795-807 (2005).</li><li>Endo, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chromatin+modification+of+Notch+targets+in+olfactory+receptor+neuron+diversification.">Chromatin modification of Notch targets in olfactory receptor neuron diversification.</a> Nat Neurosci. 15, 224-233 (2011).</li><li>Karim, M. R., Moore, A. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Morphological+analysis+of+Drosophila+larval+peripheral+sensory+neuron+dendrites+and+axons+using+genetic+mosaics.">Morphological analysis of Drosophila larval peripheral sensory neuron dendrites and axons using genetic mosaics.</a> J Vis Exp. , (2011).</li><li>Suh, G. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+single+population+of+olfactory+sensory+neurons+mediates+an+innate+avoidance+behaviour+in+Drosophila.">A single population of olfactory sensory neurons mediates an innate avoidance behaviour in Drosophila.</a> Nature. 431, 854-859 (2004).</li><li>Sachse, S., Galizia, C. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Role+of+inhibition+for+temporal+and+spatial+odor+representation+in+olfactory+output+neurons:+A+calcium+imaging+study.">Role of inhibition for temporal and spatial odor representation in olfactory output neurons: A calcium imaging study.</a> J Neurophysiol. 87, 1106-1117 (2002).</li><li>Hallem, E. A., Ho, M. G., Carlson, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+molecular+basis+of+odor+coding+in+the+Drosophila+antenna.">The molecular basis of odor coding in the Drosophila antenna.</a> Cell. 117, 965-979 (2004).</li><li>Vosshall, L. B., Wong, A. M., Axel, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+olfactory+sensory+map+in+the+fly+brain.">An olfactory sensory map in the fly brain.</a> Cell. 102, 147-159 (2000).</li><li>Couto, A., Alenius, M., Dickson, B. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular,+anatomical+and+functional+organization+of+the+Drosophila+olfactory+system.">Molecular, anatomical and functional organization of the Drosophila olfactory system.</a> Curr Biol. 15, 1535-1547 (2005).</li><li>Clyne, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Odorant+response+of+individual+sensilla+on+the+Drosophila+antenna.">Odorant response of individual sensilla on the Drosophila antenna.</a> Invert Neurosci. 3, 127-135 (1997).</li><li>Vosshall, L. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+spatial+map+of+olfactory+receptor+expression+in+the+Drosophila+antenna.">A spatial map of olfactory receptor expression in the Drosophila antenna.</a> Cell. 96, 725-736 (1999).</li><li>Wang, J. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Two-photon+calcium+imaging+reveals+an+odor-evoked+map+of+activity+in+the+fly+brain.">Two-photon calcium imaging reveals an odor-evoked map of activity in the fly brain.</a> Cell. 112, 271-282 (2003).</li></ol>

The authors have nothing to disclose.

The dissection of the Drosophila antenna we describe is simple and easy to perform in a laboratory setting. To ensure a successful dissection, it is essential to utilize fine-edged scissors. While immunostaining the dissected antenna, it is important to incubate them in a moisture-filled container to avoid evaporation of the antibody solution. The dissected antenna has a tendency to float in the solution. Using 0.1% Triton in PBS during the fixation and blocking steps will facilitate submersion of the antenna in...

The olfactory system is used to distinguish between an immense variety of odor molecules and subsequently to send the resulting information to the higher brain centers. This input is used to precisely control fundamental animal behaviors, such as feeding and mating1-6. As each olfactory neuron type is associated with a specific set of odors, the diversification of olfactory receptor neurons (ORN)s is essential for proper olfactory system function7.
Drosophila genetics enables us to perform single cell level investigation involving molecular mechanisms associated with ORN development and physiological function 8-16. Whole mount immunostaining of Drosophila antennae has enabled us to understand in greater detail the molecular mechanisms involved in the diversification of olfactory receptor neurons (ORN)s7. Herein we provide a comprehensive description of a simple method to achieve this.

<table border="0" cellpadding="0" cellspacing="0" width="606">
	<tbody>
		<tr height="41">
			<td height="41" style="height:41px;width:235px;">Stemi DV4 dissection microscope</td>
			<td style="width:143px;">Zeiss</td>
			<td style="width:113px;">Stemi DV4</td>
			<td style="width:116px;"></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:235px;">Glass bottom culture dishes&#160;</td>
			<td style="width:143px;">MatTek corporation</td>
			<td style="width:113px;">P35G-0-10-C</td>
			<td style="width:116px;"></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:235px;">Dissection scissor</td>
			<td style="width:143px;">Fine Science Tools</td>
			<td style="width:113px;">15000-08</td>
			<td style="width:116px;"></td>
		</tr>
		<tr height="61">
			<td height="61" style="height:61px;width:235px;">Rat anti-ELAV</td>
			<td style="width:143px;">Developmental Studies Hybridoma Bank</td>
			<td style="width:113px;">7E8A10</td>
			<td style="width:116px;">Dilution 1:200</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:235px;">Mouse anti-GFP</td>
			<td style="width:143px;">Invitrogen</td>
			<td style="width:113px;">A11122</td>
			<td style="width:116px;">Dilution 1:400</td>
		</tr>
		<tr height="61">
			<td height="61" style="height:61px;width:235px;">Donkey Anti-Rabbit IgG</td>
			<td style="width:143px;">Jackson ImmunoResearch Laboratories</td>
			<td style="width:113px;">711-225-152</td>
			<td style="width:116px;">Dilution 1:200</td>
		</tr>
		<tr height="61">
			<td height="61" style="height:61px;width:235px;">Donkey Anti-Rat IgG</td>
			<td style="width:143px;">Jackson ImmunoResearch Laboratories</td>
			<td style="width:113px;">712-165-150</td>
			<td style="width:116px;">Dilution 1:200</td>
		</tr>
	</tbody>
</table>

whole mount immunolabeling of olfactory receptor neurons in the drosophila antenna

Odorant molecules bind to their target receptors in a precise and coordinated manner. Each receptor recognizes a specific signal and relays this information to the brain. As such, determining how olfactory information is transferred to the brain, modifying both perception and behavior, merits investigation. Interestingly, there is emerging evidence that cellular transduction and transcriptional factors are involved in the diversification of olfactory receptor neuron. Here we provide a robust whole mount immunological labeling method to assay in vivo olfactory receptor neuron organization. Using this method, we identified all olfactory receptor neurons with anti-ELAV antibody, a known pan-neural marker and Or49a-mCD8::GFP, an olfactory receptor neuron specifically expressed in Nba neuron using anti-GFP antibody.

Ensuring that both the dissection and fixation are performed quickly is a key factor in achieving success with this protocol. Using fine scissors and forceps is also crucial. After immunostaining, fluorescent labeled antennae were examined under a confocal microscope. We normally take 1&micro;m sections using a 20x lens. We labeled Nba7 ORNs using Or49a-mCD8::GFP and counted the number of Nba ORNs in wild-type antenna. The mCD8-GFP reporter is cell membrane localized and so the expression seen in Figure 2 exhi...

Watch this Scientific Journal Video about Whole Mount Immunolabeling of Olfactory Receptor Neurons in the Drosophila Antenna at JoVE.com

Whole Mount Immunolabeling of Olfactory Receptor Neurons in the Drosophila Antenna

Herein we describe the process of whole mount immunostaining of Drosophila antennae, which enables us to better understand the molecular mechanisms involved in the diversification of olfactory receptor neurons (ORN)s.

Whole Mount Immunolabeling of Olfactory Receptor Neurons in the Drosophila Antenna

Odorant molecules bind to their target receptors in a precise and coordinated manner. Each receptor recognizes a specific signal and relays this ...

whole-mount-immunolabeling-olfactory-receptor-neurons-drosophila

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9.0K Aufrufe.  Doshisha University. Herein we describe the process of whole mount immunostaining of Drosophila antennae, which enables us to better understand the molecular mechanisms involved in the diversification of olfactory receptor neurons (ORN)s.

Serie: Whole Mount Immunolabeling of Olfactory Receptor Neurons in the Drosophila Antenna

Visualization of the Embryonic Nervous System in Whole-mount Drosophila Embryos

The Drosophila embryo is an attractive model system for investigating the cellular and molecular basis of neuronal development. Here we describe the procedure for the visualization of Drosophila embryonic nervous system using antibodies to neuronal proteins. Since the entire embryonic peripheral nervous and central nervous systems are well characterized at the level of individual cells (Dambly-Chaudi&egrave;re et al., 1986; Bodmer et al., 1987; Bodmer et al., 1989), any aberrations to these systems can be easily identified using antibodies to different neuronal proteins. The developing embryos are collected at certain times to ensure that the embryos are in the proper developmental stages for visualization. After collection, the outer layers of the embryo, the chorion membrane and the vitelline envelope that surrounds the embryo, are removed before fixation. Embryos are then incubated with neuronal antibodies and visualized using fluorescently labeled secondary antibodies. Embryos at stages 12-17 are visualized to access the embryonic nervous system. At stage 12 the CNS germ band starts shortening and by stage 15 the definitive pattern of the commissure has been achieved. By stage 17 the CNS contracts and the PNS is fully developed (Campos-Ortega et al. 1985). Thus changes in the pattern of the PNS and CNS can be easily observed during these developmental stages.

Visualization of the Embryonic Nervous System in Whole-mount Drosophila Embryos

We describe the procedure to prepare staged Drosophila embryos for the visualization of the embryonic nervous system during embryogenesis.

The Drosophila embryo is an attractive model system for investigating the cellular and molecular basis of neuronal development. Here we describe the ...

Whole Mount Preparation of the Adult Drosophila Ventral Nerve Cord for Giant Fiber Dye Injection

To analyze the axonal and dendritic morphology of neurons, it is essential to obtain accurate labeling of neuronal structures. Preparing well labeled samples with little to no tissue damage enables us to analyze cell morphology and to compare individual samples to each other, hence allowing the identification of mutant anomalies.
In the demonstrated dissection method the nervous system remains mostly inside the adult fly. Through a dorsal incision, the abdomen and thorax are opened and most of the internal organs are removed. Only the dorsal side of the ventral nerve cord (VNC) and the cervical connective 
(CvC) containing the big axons of the giant fibers (GFs)1 are exposed, while the brain containing the GF cell body and dendrites remains2 in the 
intact head. In this preparation most nerves of the VNC should remain attached to their muscles. 
Following the dissection, the intracellular filling of the giant fiber (GF) with a fluorescent dye is demonstrated. In the CvC the GF axons are located at the dorsal surface and thus can be easily visualized under a microscope with differential interference contrast (DIC) optics. This allows the injection of the GF axons with dye at this site to label the entire GF including the axons and their terminals in the VNC. This method results in reliable and strong staining of the GFs allowing the neurons to be imaged immediately after filling with an epifluorescent microscope. Alternatively, the fluorescent signal can be enhanced using standard immunohistochemistry procedures3 suitable for high resolution confocal microscopy.

Whole Mount Preparation of the Adult Drosophila Ventral Nerve Cord for Giant Fiber Dye Injection

An in vivo dissection of the adult Drosophila ventral nerve cord (VNC) is demonstrated. This particular dissection method causes little damage to the VNC allowing the subsequent labeling of the giant fiber neurons with fluorescent dye for high resolution imaging.

To analyze the axonal and dendritic morphology of neurons, it is essential to obtain accurate labeling of neuronal structures. Preparing well labeled ...

Flash Photolysis of Caged Compounds in the Cilia of Olfactory Sensory  Neurons

Photolysis of caged compounds allows the production of rapid and localized increases in the concentration of various physiologically active compounds1. Caged compounds are molecules made physiologically inactive by a chemical cage that can be broken by a flash of ultraviolet light. Here, we show how to obtain patch-clamp recordings combined with photolysis of caged compounds for the study of olfactory transduction in dissociated mouse olfactory sensory neurons. The process of olfactory transduction (Figure 1) takes place in the cilia of olfactory sensory neurons, where odorant binding to receptors leads to the increase of cAMP that opens cyclic nucleotide-gated (CNG) channels2. Ca entry through CNG channels activates Ca-activated Cl channels. We show how to dissociate neurons from the mouse olfactory epithelium3 and how to activate CNG channels or Ca-activated Cl channels by photolysis of caged cAMP4 or caged Ca5. We use a flash lamp6,7 to apply ultraviolet flashes to the ciliary region to uncage cAMP or Ca while patch-clamp recordings are taken to measure the current in the whole-cell voltage-clamp configuration8-11.

Photolysis of caged compounds allows the production of rapid and localized increases in the concentration of various physiologically active compounds. Here, we show how to obtain patch-clamp recordings combined with photolysis of caged cAMP or caged Ca for the study of olfactory transduction in dissociated mouse olfactory sensory neurons.

Photolysis of caged compounds allows the production of rapid and localized increases in the concentration of various physiologically active compounds1. ...

DiI-Labeling of DRG Neurons to Study Axonal Branching in a Whole Mount Preparation of Mouse Embryonic Spinal Cord

Here we present a technique to label the trajectories of small groups of DRG neurons into the embryonic spinal cord by diffusive staining using the lipophilic tracer 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI)1. The comparison of axonal pathways of wild-type with those of mouse lines in which genes are mutated allows testing for a functional role of candidate proteins in the control of axonal branching which is an essential mechanism in the wiring of the nervous system. Axonal branching enables an individual neuron to connect with multiple targets, thereby providing the physical basis for the parallel processing of information. Ramifications at intermediate target regions of axonal growth may be distinguished from terminal arborization. Furthermore, different modes of axonal branch formation may be classified depending on whether branching results from the activities of the growth cone (splitting or delayed branching) or from the budding of collaterals from the axon shaft in a process called interstitial branching2 (Fig. 1).
The central projections of neurons from the DRG offer a useful experimental system to study both types of axonal branching: when their afferent axons reach the dorsal root entry zone (DREZ) of the spinal cord between embryonic days 10 to 13 (E10 - E13) they display a stereotyped pattern of T- or Y-shaped bifurcation. The two resulting daughter axons then proceed in rostral or caudal directions, respectively, at the dorsolateral margin of the cord and only after a waiting period collaterals sprout from these stem axons to penetrate the gray matter (interstitial branching) and project to relay neurons in specific laminae of the spinal cord where they further arborize (terminal branching)3. DiI tracings have revealed growth cones at the dorsal root entry zone of the spinal cord that appeared to be in the process of splitting suggesting that bifurcation is caused by splitting of the growth cone itself4 (Fig. 2), however, other options have been discussed as well5.
This video demonstrates first how to dissect the spinal cord of E12.5 mice leaving the DRG attached. Following fixation of the specimen tiny amounts of DiI are applied to DRG using glass needles pulled from capillary tubes. After an incubation step, the labeled spinal cord is mounted as an inverted open-book preparation to analyze individual axons using fluorescence microscopy.

The stereotyped projections of sensory afferents into the rodent spinal cord offer an easily accessible experimental system to study axonal branching through the tracing of single axons.

Here we  present a technique to label the trajectories of small groups of DRG neurons  into the embryonic spinal cord by diffusive staining using the ...

Odorant-induced Responses Recorded from Olfactory Receptor Neurons using the Suction Pipette Technique

Animals sample the odorous environment around them through the chemosensory systems located in the nasal cavity. Chemosensory signals affect complex behaviors such as food choice, predator, conspecific and mate recognition and other socially relevant cues. Olfactory receptor neurons (ORNs) are located in the dorsal part of the nasal cavity embedded in the olfactory epithelium. These bipolar neurons send an axon to the olfactory bulb (see Fig. 1, Reisert &amp; Zhao1, originally published in the Journal of General Physiology) and extend a single dendrite to the epithelial border from where cilia radiate into the mucus that covers the olfactory epithelium. The cilia contain the signal transduction machinery that ultimately leads to excitatory current influx through the ciliary transduction channels, a cyclic nucleotide-gated (CNG) channel and a Ca2+-activated Cl- channel (Fig. 1). The ensuing depolarization triggers action potential generation at the cell body2-4.
In this video we describe the use of the "suction pipette technique" to record odorant-induced responses from ORNs. This method was originally developed to record from rod photoreceptors5 and a variant of this method can be found at jove.com modified to record from mouse cone photoreceptors6. The suction pipette technique was later adapted to also record from ORNs7,8. Briefly, following dissociation of the olfactory epithelium and cell isolation, the entire cell body of an ORN is sucked into the tip of a recording pipette. The dendrite and the cilia remain exposed to the bath solution and thus accessible to solution changes to enable e.g. odorant or pharmacological blocker application. In this configuration, no access to the intracellular environment is gained (no whole-cell voltage clamp) and the intracellular voltage remains free to vary. This allows the simultaneous recording of the slow receptor current that originates at the cilia and fast action potentials fired by the cell body9. The difference in kinetics between these two signals allows them to be separated using different filter settings. This technique can be used on any wild type or knockout mouse or to record selectively from ORNs that also express GFP to label specific subsets of ORNs, e.g. expressing a given odorant receptor or ion channel.

Olfactory receptor neurons (ORNs) convert odor signals first into a receptor current that in turn triggers action potentials that are conveyed to second order neurons in the olfactory bulb. Here we describe the suction pipette technique to record simultaneously the odorant-induced receptor current and action potentials from mouse ORNs.

Animals sample the odorous environment around them through the chemosensory systems located in the nasal cavity. Chemosensory signals affect complex ...

Appetitive Associative Olfactory Learning in Drosophila Larvae

In the following we describe the methodological details of appetitive associative olfactory learning in Drosophila larvae. The setup, in combination with genetic interference, provides a handle to analyze the neuronal and molecular fundamentals of specifically associative learning in a simple larval brain.
Organisms can use past experience to adjust present behavior. Such acquisition of behavioral potential can be defined as learning, and the physical bases of these potentials as memory traces1-4. Neuroscientists try to understand how these processes are organized in terms of molecular and neuronal changes in the brain by using a variety of methods in model organisms ranging from insects to vertebrates5,6. For such endeavors it is helpful to use model systems that are simple and experimentally accessible. The Drosophila larva has turned out to satisfy these demands based on the availability of robust behavioral assays, the existence of a variety of transgenic techniques and the elementary organization of the nervous system comprising only about 10,000 neurons (albeit with some concessions: cognitive limitations, few behavioral options, and richness of experience questionable)7-10.
Drosophila larvae can form associations between odors and appetitive gustatory reinforcement like sugar11-14. In a standard assay, established in the lab of B. Gerber, animals receive a two-odor reciprocal training: A first group of larvae is exposed to an odor A together with a gustatory reinforcer (sugar reward) and is subsequently exposed to an odor B without reinforcement 9. Meanwhile a second group of larvae receives reciprocal training while experiencing odor A without reinforcement and subsequently being exposed to odor B with reinforcement (sugar reward). In the following both groups are tested for their preference between the two odors. Relatively higher preferences for the rewarded odor reflect associative learning - presented as a performance index (PI). The conclusion regarding the associative nature of the performance index is compelling, because apart from the contingency between odors and tastants, other parameters, such as odor and reward exposure, passage of time and handling do not differ between the two groups9.

Appetitive Associative Olfactory Learning in Drosophila Larvae

Drosophila larvae are able to associate odor stimuli with gustatory reward. Here we describe a simple behavioral paradigm that allows the analysis of appetitive associative olfactory learning.

In the following we describe the methodological  details of appetitive associative olfactory learning in Drosophila larvae. The setup, in combination with ...

Assessing Neurodegenerative Phenotypes in Drosophila Dopaminergic Neurons by Climbing Assays and Whole Brain Immunostaining

Drosophila melanogaster is a valuable model organism to study aging and pathological degenerative processes in the nervous system. The advantages of the fly as an experimental system include its genetic tractability, short life span and the possibility to observe and quantitatively analyze complex behaviors. The expression of disease-linked genes in specific neuronal populations of the Drosophila brain, can be used to model human neurodegenerative diseases such as Parkinson's and Alzheimer's 5.
Dopaminergic (DA) neurons are among the most vulnerable neuronal populations in the aging human brain. In Parkinson's disease (PD), the most common neurodegenerative movement disorder, the accelerated loss of DA neurons leads to a progressive and irreversible decline in locomotor function. In addition to age and exposure to environmental toxins, loss of DA neurons is exacerbated by specific mutations in the coding or promoter regions of several genes. The identification of such PD-associated alleles provides the experimental basis for the use of Drosophila as a model to study neurodegeneration of DA neurons in vivo. For example, the expression of the PD-linked human &alpha;-synuclein gene in Drosophila DA neurons recapitulates some features of the human disease, e.g. progressive loss of DA neurons and declining locomotor function 2. Accordingly, this model has been successfully used to identify potential therapeutic targets in PD 8.
Here we describe two assays that have commonly been used to study age-dependent neurodegeneration of DA neurons in Drosophila: a climbing assay based on the startle-induced negative geotaxis response and tyrosine hydroxylase immunostaining of whole adult brain mounts to monitor the number of DA neurons at different ages. In both cases, in vivo expression of UAS transgenes specifically in DA neurons can be achieved by using a tyrosine hydroxylase (TH) promoter-Gal4 driver line 3, 10.

Assessing Neurodegenerative Phenotypes in Drosophila Dopaminergic Neurons by Climbing Assays and Whole Brain Immunostaining

Here we describe two assays that have been established to study age-dependent neurodegeneration of dopaminergic (DA) neurons in Drosophila: the climbing/startle-induced negative geotaxis assay which allows to study the functional effects of DA neurons degeneration and the tyrosine hydroxylase immunostaining which is used to identify and count DA neurons in whole brain mounts.

Drosophila melanogaster is a valuable model organism to study aging and pathological degenerative processes in the nervous system. The advantages of the ...

Whole Mount Labeling of Cilia in the Main Olfactory System of Mice

The mouse olfactory system comprises 6-10 million olfactory sensory neurons in the epithelium lining the nasal cavity. Olfactory neurons extend a single dendrite to the surface of the epithelium, ending in a structure called dendritic knob. Cilia emanate from this knob into the mucus covering the epithelial surface. The proteins of the olfactory signal transduction cascade are mainly localized in the ciliary membrane, being in direct contact with volatile substances in the environment. For a detailed understanding of olfactory signal transduction, one important aspect is the exact morphological analysis of signaling protein distribution. Using light microscopical approaches in conventional cryosections, protein localization in olfactory cilia is difficult to determine due to the density of ciliary structures. To overcome this problem, we optimized an approach for whole mount labeling of cilia, leading to improved visualization of their morphology and the distribution of signaling proteins. We demonstrate the power of this approach by comparing whole mount and conventional cryosection labeling of Kirrel2. This axon-guidance adhesion molecule is known to localize in a subset of sensory neurons and their axons in an activity-dependent manner. Whole mount cilia labeling revealed an additional and novel picture of the localization of this protein.

Cilia of olfactory sensory neurons contain proteins of the signal transduction cascade, but a detailed spatial analysis of their distribution is difficult in cryosections. We describe here an optimized approach for whole mount labeling and en face visualization of ciliary proteins.

The mouse olfactory system comprises 6-10 million olfactory sensory neurons in the epithelium lining the nasal cavity. Olfactory neurons extend a single ...

Perforated Patch-clamp Recording of Mouse Olfactory Sensory Neurons in Intact Neuroepithelium: Functional Analysis of Neurons Expressing an Identified Odorant Receptor

Analyzing the physiological responses of olfactory sensory neurons (OSN) when stimulated with specific ligands is critical to understand the basis of olfactory-driven behaviors and their modulation. These coding properties depend heavily on the initial interaction between odor molecules and the olfactory receptor (OR) expressed in the OSNs. The identity, specificity and ligand spectrum of the expressed OR are critical. The probability to find the ligand of the OR expressed in an OSN chosen randomly within the epithelium is very low. To address this challenge, this protocol uses genetically tagged mice expressing the fluorescent protein GFP under the control of the promoter of defined ORs. OSNs are located in a tight and organized epithelium lining the nasal cavity, with neighboring cells influencing their maturation and function. Here we describe a method to isolate an intact olfactory epithelium and record through patch-clamp recordings the properties of OSNs expressing defined odorant receptors. The protocol allows one to characterize OSN membrane properties while keeping the influence of the neighboring tissue. Analysis of patch-clamp results yields&#160;a precise quantification of ligand/OR interactions, transduction pathways and pharmacology, OSNs&#39; coding properties and their modulation at the membrane level.&#160;

Analyzing the physiological properties of olfactory sensory neurons still faces technical limitations. Here we record them through perforated patch-clamp in an intact preparation of the olfactory epithelium in gene-targeted mice. This technique allows the characterization of membrane properties and responses to specific ligands of neurons expressing defined olfactory receptors.

Analyzing the physiological responses of olfactory sensory neurons (OSN) when stimulated with specific ligands is critical to understand the basis of ...

Whole Mount Dissection and Immunofluorescence of the Adult Mouse Cochlea

The organ of Corti, housed in the cochlea of the inner ear, contains mechanosensory hair cells and surrounding supporting cells which are organized in a spiral shape and have a tonotopic gradient for sound detection. The mouse cochlea is approximately 6 mm long and often divided into three turns (apex, middle, and base) for analysis. To investigate cell loss, cell division, or mosaic gene expression, the whole mount or surface preparation of the cochlea is useful. This dissection method allows visualization of all cells within the organ of Corti when combined with immunostaining and confocal microscopy to image cells at different planes in the z-axis. Multiple optical cross-sections can also be obtained from these z-stack images. In addition, the whole mount dissection method can be used for scanning electron microscopy, although a different fixation method is needed. Here, we present a method to isolate the organ of Corti as three intact cochlear turns (apex, middle, and base). This method can be used for mice ranging from one week of age through adulthood and differs from the technique used for neonatal samples where calcification of the cochlea is incomplete. A slightly modified version can be used for dissection of the rat cochlea. We also demonstrate a procedure for immunostaining with fluorescently tagged antibodies.

We present a method to isolate the adult organ of Corti as three intact cochlear turns (apex, middle, and base). We also demonstrate a procedure for immunostaining with fluorescently tagged antibodies. Together these techniques allow the study of hair cells, supporting cells, and other cell types found in the cochlea.

The organ of Corti, housed in the cochlea of the inner ear, contains mechanosensory hair cells and surrounding supporting cells which are organized in a ...