Name: methods for studying the mechanisms of action of antipsychotic drugs in caenorhabditis elegans
Uploaded: 2014-02-04T14:00:00
Description: Watch this Scientific Journal Video about Methods for Studying the Mechanisms of Action of Antipsychotic Drugs in Caenorhabditis elegans at JoVE.com

The work was supported by an NIH Clinical Scientist Development award K08NS002083, a Shervert Frazier Research Institute Grant, and a NARSAD Young Investigator Award to Edgar A. Buttner.

1. Developmental Delay/Lethality Assay: The Wild-Type (N2) and Two Mutant (Mut1 and Mut2) Strains Are Tested in Three Clozapine Concentrations in a 12-well Plate
<ol>
	<li>On day 1, pour 2 ml NGM medium10 into each well of a 12-well plate (each well with a 2 cm diameter) and allow to harden on the bench at room temperature (RT) overnight. The same day, pick a colony of Escherichia coli OP50 bacteria, infect a bottle of 50 ml LB solution, and culture it in a 37 &#176;C shaker at 220...

<ol>
	<li>Donohoe, D. R., Jarvis, R. A., Weeks, K., Aamodt, E. J., Dwyer, D. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Behavioral+adaptation+in+C.+elegans+produced+by+antipsychotic+drugs+requires+serotonin+and+is+associated+with+calcium+signaling+and+calcineurin+inhibition.">Behavioral adaptation in C. elegans produced by antipsychotic drugs requires serotonin and is associated with calcium signaling and calcineurin inhibition.</a> Neurosci. 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S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Antipsychotic+drugs+disrupt+normal+development+in+Caenorhabditis+elegans+via+additional+mechanisms+besides+dopamine+and+serotonin+receptors.">Antipsychotic drugs disrupt normal development in Caenorhabditis elegans via additional mechanisms besides dopamine and serotonin receptors.</a> Pharmacol. Res. 54, 361-372 (2006).</li><li>Karmacharya, R., 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=Behavioral+effects+of+clozapine:+involvement+of+trace+amine+pathways+in+C.+elegans+and+M.+musculus.">Behavioral effects of clozapine: involvement of trace amine pathways in C. elegans and M. musculus.</a> Brain Res. 1393, 91-99 (2011).</li><li>Saur, T., 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+Genome-Wide+RNAi+Screen+in+Caenorhabditis+elegans+Identifies+the+Nicotinic+Acetylcholine+Receptor+Subunit+ACR-7+as+an+Antipsychotic+Drug+Target.">A Genome-Wide RNAi Screen in Caenorhabditis elegans Identifies the Nicotinic Acetylcholine Receptor Subunit ACR-7 as an Antipsychotic Drug Target.</a> PLoS Genet. 9, (2013).</li><li>Avery, L., You, Y. 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H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+developmental+exposure+to+ethanol+on+Caenorhabditis+elegans.">Effects of developmental exposure to ethanol on Caenorhabditis elegans.</a> Alcohol Clin. Exp. Res. 32, 853-867 (2008).</li><li>Kage-Nakadai, E., 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+very+long+chain+fatty+acid+acyl-CoA+synthetase+genes,+acs-20+and+acs-22,+have+roles+in+the+cuticle+surface+barrier+in+Caenorhabditis+elegans.">Two very long chain fatty acid acyl-CoA synthetase genes, acs-20 and acs-22, have roles in the cuticle surface barrier in Caenorhabditis elegans.</a> PLoS One. 5, (2010).</li><li>Partridge, F. A., Tearle, A. W., Gravato-Nobre, M. J., Schafer, W. 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Here, we describe methods for testing the effects of APDs on the development and behavior of C. elegans. DMSO or ethanol is used to dissolve clozapine, since the drug is relatively insoluble in water. Because solvents have been reported to affect C. elegans biology12, DMSO-alone or ethanol-alone control groups are essential. The highest concentration of DMSO used in our assays is up to 3%, which does not have an obvious effect on C. elegans development. DMSO can be used for many smal...

Caenorhabditis elegans is a simple genetic organism amenable to large-scale forward and reverse genetic screens and chemical genetic screens. C. elegans is sensitive to a wide spectrum of bioactive compounds and has therefore been used successfully to define the mechanisms of action of a variety of such compounds. For example, bioactive compounds studied using worm pharmacogenetics include acetylcholine receptor agonists (e.g.&#160;levamisole, nicotine, morantel, and pyrantel), anesthetics (e.g.&#160;halothane), caffeine, cholinesterase inhibitors (e.g.&#160;aldicarb, lannate, and trichlorfon), fluoride, GABA-related compounds (e.g.&#160;GABA and muscimol), ivermectin, paraquat, phorbol esters, and serotonin-related drugs (e.g.&#160;serotonin and imiprimine)3. Furthermore, C. elegans has been used for large-scale small molecule screens, allowing discovery of new bioactive compounds and identification of novel genetic targets4.
The C. elegans genome includes potential antipsychotic drug (APD) targets conserved in humans, including genes encoding proteins required for neurotransmitter synthesis and for synaptic structure and function5. Thus, C. elegans neurogenetics and neurobiology offer methods for discovering novel molecular mechanisms of action of APDs. In nematodes, APD exposure early in development produces developmental delay, and at higher concentrations, lethality2,6. APD exposure during adulthood produces behavioral phenotypes. For example, clozapine exposure inhibits locomotion and pharyngeal pumping and enhances egg laying1,2,7.
APD-induced developmental delay and lethality are powerful phenotypes for large-scale chemical genetic screens. These phenotypes are complex in so far as they likely have more than one cellular and genetic basis. Therefore, such genetic screens are expected to yield a variety of indirect drug targets. However, our laboratory has conducted candidate gene screens and a genome-wide RNAi screen for suppressors of APD-induced developmental delay and lethality and has successfully recovered genes which likely encode direct targets, including dopamine, insulin, and nicotinic acetylcholine receptors2,8. Genetic screens based on APD-induced behaviors in the adult have also led to the identification of novel APD targets, and we are now validating targets from both developmental and behavioral screens in mammals7. Thus, an invertebrate chemical genetic approach to discover novel molecular mechanisms of action of APDs appears to be feasible5,8.
The C. elegans pharynx is an organ that includes 20 neurons, 20 muscle cells, and 20 accessory cells, wrapped by a basement membrane. Similar to the mammalian heart, the pharynx is autonomous and constantly pumps food in from the external environment9. Inhibition of the pharyngeal pumping rate compromises food uptake, and thus mutations or drugs that inhibit pharyngeal pumping cause developmental delay or arrest9. APDs inhibit the pharyngeal pumping rate, accounting in part for their effects on development and viability1,2. Here, we use the atypical APD clozapine as an example to demonstrate drug assays for nematode development and pharyngeal pumping.

<table border="0" cellpadding="0" cellspacing="0" width="406">
	<tbody>
		<tr height="22">
			<td>Clozapine</td>
			<td>Sigma</td>
			<td>C6305</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:216px;">Dimethyl sulfoxide (DMSO)</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:119px;">D8418</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:216px;">Acetic acid (HAC)</td>
			<td style="width:71px;">Fisher</td>
			<td style="width:119px;">BP2401</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:216px;">Sodium hydroxide(NaOH)</td>
			<td style="width:71px;">EMD</td>
			<td style="width:119px;">SX0590-13</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:216px;">Hypochlorite</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">425044</td>
		</tr>
		<tr height="32">
			<td height="32" style="height:32px;width:236px;">Centrifuge 5810</td>
			<td style="width:188px;">Eppendorf</td>
			<td style="width:200px;">5810 000.017</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:236px;">Incubator shaker</td>
			<td style="width:188px;">New Brunswick Scientific</td>
			<td style="width:200px;">M1246-0006</td>
		</tr>
		<tr height="31">
			<td height="31" style="height:31px;width:236px;">Low temperature incubator 815</td>
			<td style="width:188px;">Precision Scientific</td>
			<td style="width:200px;">J1790-1B</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:236px;">Stereo microscope</td>
			<td style="width:188px;">Olympus</td>
			<td style="width:200px;">SZX12</td>
		</tr>
		<tr height="38">
			<td height="38" style="height:38px;width:236px;">Petri dish 35 x 10 mm</td>
			<td style="width:188px;">Fisher Scientific</td>
			<td style="width:200px;">NC9434271</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:236px;">12-well tissue culture plate</td>
			<td style="width:188px;">BD Falcon</td>
			<td style="width:200px;">REF 353043</td>
		</tr>
	</tbody>
</table>

methods for studying the mechanisms of action of antipsychotic drugs in caenorhabditis elegans

Caenorhabditis elegans is a simple genetic organism amenable to large-scale forward and reverse genetic screens and chemical genetic screens. The C. elegans genome includes potential antipsychotic drug (APD) targets conserved in humans, including genes encoding proteins required for neurotransmitter synthesis and for synaptic structure and function. APD exposure produces developmental delay and/or lethality in nematodes in a concentration-dependent manner. These phenotypes are caused, in part, by APD-induced inhibition of pharyngeal pumping1,2. Thus, the developmental phenotype has a neuromuscular basis, making it useful for pharmacogenetic studies of neuroleptics. Here we demonstrate detailed procedures for testing APD effects on nematode development and pharyngeal pumping. For the developmental assay, synchronized embryos are placed on nematode growth medium (NGM) plates containing APDs, and the stages of developing animals are then scored daily. For the pharyngeal pumping rate assay, staged young adult animals are tested on NGM plates containing APDs. The number of pharyngeal pumps per unit time is recorded, and the pumping rate is calculated. These assays can be used for studying many other types of small molecules or even large molecules.

1. Developmental delay/lethality assay result
A typical result for the developmental delay/lethality assay is demonstrated in Figures&#160;1a and 1b. When wild-type animals in the control group have grown to the gravid adult stage (Figure&#160;1a), wild-type animals exposed to clozapine are still in the young larval stages or are dead (Figure&#160;1b). Figure&#160;1c shows a representative result comparing a supp...

Watch this Scientific Journal Video about Methods for Studying the Mechanisms of Action of Antipsychotic Drugs in Caenorhabditis elegans at JoVE.com

Methods for Studying the Mechanisms of Action of Antipsychotic Drugs in Caenorhabditis elegans

Approaches for testing the effects of antipsychotic drugs (APDs) in Caenorhabditis elegans are demonstrated. Assays are described for testing drug effects on development and viability and on pharyngeal pumping rate. These methods are also applicable for pharmacogenetic experiments with drug classes other than APDs.

Methods for Studying the Mechanisms of Action of Antipsychotic Drugs in Caenorhabditis elegans

Caenorhabditis elegans is a simple genetic organism amenable to  large-scale forward and reverse genetic screens and chemical genetic screens. The C.  ...

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Neuroscience

Mouse in Utero Electroporation: Controlled Spatiotemporal Gene Transfection

In order to understand the function of genes expressed in specific region of the developing brain, including signaling molecules and axon guidance molecules, local gene transfer or knock- out is required. Gene targeting knock-in or knock-out into local regions is possible to perform with combination with a specific CRE line, which is laborious, costly, and time consuming. Therefore, a simple transfection method, an in utero electroporation technique, which can be performed with short time, will be handy to test the possible function of candidate genes prior to the generation of transgenic animals 1,2. In addition to this, in utero electroporation targets areas of the brain where no specific CRE line exists, and will limit embryonic lethality 3,4. Here, we present a method of in utero electroporation combining two different types of electrodes for simple and convenient gene transfer into target areas of the developing brain. First, a unique holding method of embryos using an optic fiber optic light cable will make small embryos (from E9.5) visible for targeted DNA solution injection into ventricles and needle type electrodes insertion to the targeted brain area 5,6. The patterning of the brain such as cortical area occur at early embryonic stage, therefore, these early electroporation from E9.5 make a big contribution to understand entire area patterning event. Second, the precise shape of a capillary prevents uterine damage by making holes by insertion of the capillary. Furthermore, the precise shape of the needle electrodes are created with tungsten and platinum wire and sharpened using sand paper and insulated with nail polish 7, a method which is described in great detail in this protocol. This unique technique allows transfection of plasmid DNA into restricted areas of the brain and will enable small embryos to be electroporated. This will help to, open a new window for many scientists who are working on cell differentiation, cell migration, axon guidance in very early embryonic stage. Moreover, this technique will allow scientists to transfect plasmid DNA into deep parts of the developing brain such as thalamus and hypothalamus, where not many region-specific CRE lines exist for gain of function (GOF) or loss of function (LOF) analyses.

Mouse in Utero Electroporation: Controlled Spatiotemporal Gene Transfection

A gene transfer method into the developing mouse brain is described by using a unique surgical method and special shape of electrodes. This unique technique allows transfection of plasmid DNA temporally and spatially, which will aid many neuroscientists in studying brain development.

In order to understand the function of genes expressed in specific region of the developing brain, including signaling molecules and axon guidance ...

Direct Intraventricular Delivery of Drugs to the Rodent Central Nervous System

Due to an inability to cross the blood brain barrier, certain drugs need to be directly delivered into the central nervous system (CNS). Our lab focuses specifically on antisense oligonucleotides (ASOs), though the techniques shown in the video here can also be used to deliver a plethora of other drugs to the CNS. Antisense oligonucleotides (ASOs) have the capability to knockdown sequence-specific targets 1 as well as shift isoform ratios of specific genes 2. To achieve widespread gene knockdown or splicing in the CNS of mice, the ASOs can be delivered into the brain using two separate routes of administration, both of which we demonstrate in the video.
The first uses Alzet osmotic pumps, connected to a catheter that is surgically implanted into the lateral ventricle. This allows the ASOs to be continuously infused into the CNS for a designated period of time. The second involves a single bolus injection of a high concentration of ASO into the right lateral ventricle. Both methods use the mouse cerebral ventricular system to deliver the ASO to the entire brain and spinal cord, though depending on the needs of the study, one method may be preferred over the other.

We describe a method to target drugs to the central nervous system by either implanting a catheter or performing a bolus injection into the right lateral ventricle in mice. We focus specifically on the delivery of antisense oligonucleotides. This technique is readily adaptable to other drugs and to rats.

Due to an inability to cross the blood brain barrier, certain drugs need to be directly delivered into the central nervous system (CNS). Our lab focuses ...

A Caenorhabditis elegans Model System for Amylopathy Study

Amylopathy is a term that describes abnormal synthesis and accumulation of amyloid beta (A&beta;) in tissues with time. A&beta; is a hallmark of Alzheimer's disease (AD) and is found in Lewy body dementia, inclusion body myositis and cerebral amyloid angiopathy 1-4. Amylopathies progressively develop with time. For this reason simple organisms with short lifespans may help to elucidate molecular aspects of these conditions. Here, we describe experimental protocols to study A&beta;-mediated neurodegeneration using the worm Caenorhabditis elegans. Thus, we construct transgenic worms by injecting DNA encoding human A&beta;42 into the syncytial gonads of adult hermaphrodites. Transformant lines are stabilized by a mutagenesis-induced integration. Nematodes are age synchronized by collecting and seeding their eggs. The function of neurons expressing A&beta;42 is tested in opportune behavioral assays (chemotaxis assays). Primary neuronal cultures obtained from embryos are used to complement behavioral data and to test the neuroprotective effects of anti-apoptotic compounds.

A Caenorhabditis elegans Model System for Amylopathy Study

We describe methods to study aspects of amylopathies in the worm C. elegans. We show how to construct worms expressing human A&beta;42 in neurons and how to test their function in behavioral assays. We further show how to obtain primary neuronal cultures that can be used for pharmacological testing.

Amylopathy is a term that describes abnormal synthesis and accumulation of amyloid beta (A&beta;) in tissues with time. A&beta; is a hallmark of ...

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.

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.

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

An Assay for Measuring the Effects of Ethanol on the Locomotion Speed of Caenorhabditis elegans

Alcohol use disorders are a significant public health concern, for which there are few effective treatment strategies. One difficulty that has delayed the development of more effective treatments is the relative lack of understanding of the molecular underpinnings of the effects of ethanol on behavior. The nematode, Caenorhabditis elegans (C.&#160;elegans), provides a useful model in which to generate and test hypotheses about the molecular effects of ethanol. Here, we describe an assay that has been developed and used to examine the roles of particular genes and environmental factors in behavioral responses to ethanol, in which locomotion is the behavioral output. Ethanol dose-dependently causes an acute depression of crawling on an agar surface. The effects are dynamic; animals exposed to a high concentration demonstrate an initial strong depression of crawling, referred to here as initial sensitivity, and then partially recover locomotion speed despite the continued presence of the drug. This ethanol-induced behavioral plasticity is referred to here as the development of acute functional tolerance. This assay has been used to demonstrate that these two phenotypes are distinct and genetically separable. The straightforward locomotion assay described here is suitable for examining the effects of both genetic and environmental manipulations on these acute behavioral responses to ethanol in C.&#160;elegans.

An Assay for Measuring the Effects of Ethanol on the Locomotion Speed of Caenorhabditis elegans

C. elegans is a useful model for studying the effects of ethanol on behavior. We present a behavioral assay that quantifies the effects of ethanol on the locomotion speed of crawling worms; both initial sensitivity and the development of acute functional tolerance to ethanol can be measured with this assay.

Alcohol use disorders are a significant public health concern, for which there are few effective treatment strategies. One difficulty that has delayed the ...

Agarose Microchambers for Long-term Calcium Imaging of Caenorhabditis elegans

Behavior is controlled by the nervous system. Calcium imaging is a straightforward method in the transparent nematode Caenorhabditis elegans to measure the activity of neurons during various behaviors. To correlate neural activity with behavior, the animal should not be immobilized but should be able to move. Many behavioral changes occur during long time scales and require recording over many hours of behavior. This also makes it necessary to culture the worms in the presence of food. How can worms be cultured and their neural activity imaged over long time scales? Agarose Microchamber Imaging (AMI) was previously developed to culture and observe small larvae and has now been adapted to study all life stages from early L1 until the adult stage of C. elegans. AMI can be performed on various life stages of C. elegans. Long-term calcium imaging is achieved without immobilizing the animals by using short externally triggered exposures combined with an electron multiplying charge-coupled device (EMCCD) camera recording. Zooming out or scanning can scale up this method to image up to 40 worms in parallel. Thus, a method is described to image behavior and neural activity over long time scales in all life stages of C. elegans.

Agarose Microchambers for Long-term Calcium Imaging of Caenorhabditis elegans

Imaging behavior and neural activity over long time scales without immobilization of the animal is a prerequisite to understand behavior. Agarose microfluidic chambers imaging (AMI) can be used to image neural activity and behavior for all life stages of Caenorhabditis elegans.

Behavior is controlled by the nervous system. Calcium imaging is a straightforward method in the transparent nematode Caenorhabditis elegans to measure ...

Novel Metrics to Characterize Embryonic Elongation of the Nematode Caenorhabditis elegans

Dissecting the signaling pathways that control the alteration of morphogenic processes during embryonic development requires robust and sensitive metrics. Embryonic elongation of the nematode Caenorhabditis elegans is a late developmental stage consisting of the elongation of the embryo along its longitudinal axis. This developmental stage is controlled by intercellular communication between hypodermal cells and underlying body-wall muscles. These signaling mechanisms control the morphology of hypodermal cells by remodeling the cytoskeleton and the cell-cell junctions. Measurement of embryonic lethality and developmental arrest at larval stages as well as alteration of cytoskeleton and cell-cell adhesion structures in hypodermal and muscle cells are classical phenotypes that have been used for more than 25 years to dissect these signaling pathways. Recent studies required the development of novel metrics specifically targeting either early or late elongation and characterizing morphogenic defects along the antero-posterior axis of the embryo. Here, we provide detailed protocols enabling the accurate measurement of the length and the width of the elongating embryos as well as the length of synchronized larvae. These methods constitute useful tools to identify genes controlling elongation, to assess whether these genes control both early and late phases of this stage and are required evenly along the antero-posterior axis of the embryo.

Novel Metrics to Characterize Embryonic Elongation of the Nematode Caenorhabditis elegans

Here we detail protocols specifically designed to monitor morphogenic defects that occur during early and late phases of embryonic elongation of the nematode Caenorhabditis elegans. Ultimately, these protocols are designed to identify genes that regulate these phases and to characterize their differential requirements along the antero-posterior axis of the embryo.

Dissecting the signaling pathways that control the alteration of morphogenic processes during embryonic development requires robust and sensitive metrics. ...

A Caenorhabditis elegans Nutritional-status Based Copper Aversion Assay

To ensure survival, organisms must be capable of avoiding unfavorable habitats while ensuring a consistent food source. Caenorhabditis elegans alter their locomotory patterns upon detection of diverse environmental stimuli and can modulate their suite of behavioral responses in response to starvation conditions. Nematodes typically exhibit a decreased aversive response when removed from a food source for over 30 min. Observation of behavioral changes in response to a changing nutritional status can provide insight into the mechanisms that regulate the transition from a well-fed to starved state.
We have developed an assay that measures a nematode&#39;s ability to cross an aversive barrier (i.e. copper) then reach a food source over a prolonged period of time. This protocol builds upon previous work by integrating multiple variables in a manner that allows for continued data collection as the organisms shift towards an increasingly starved condition. Moreover, this assay permits an increased sample size so that larger populations of nematodes can be simultaneously evaluated.
Organisms defective for the ability to detect or respond to copper immediately cross the chemical barrier, while wild type nematodes are initially repelled. As wild type worms are increasingly starved, they begin to cross the barrier and reach the food source. We designed this assay to evaluate a mutant that is incapable of responding to diverse environmental cues, including food sensation or detection of aversive chemicals. When evaluated via this protocol, the defective organisms immediately crossed the barrier, but were also incapable of detecting a food source. Hence, these mutants repeatedly cross the chemical barrier despite temporarily reaching a food source. This assay can straightforwardly test populations of worms to evaluate potential pathway defects related to aversion and starvation.

A Caenorhabditis elegans Nutritional-status Based Copper Aversion Assay

Here, we present a Caenorhabditis elegans-specific assay designed to evaluate changes in copper aversion behavior and the ability to locate a common food source, as the organism progresses from a well-fed to starved nutritional state.

To ensure survival, organisms must be capable of avoiding unfavorable habitats while ensuring a consistent food source. Caenorhabditis elegans alter their ...

Ratiometric Calcium Imaging of Individual Neurons in Behaving Caenorhabditis Elegans

It has become increasingly clear that neural circuit activity in behaving animals differs substantially from that seen in anesthetized or immobilized animals. Highly sensitive, genetically encoded fluorescent reporters of Ca2+ have revolutionized the recording of cell and synaptic activity using non-invasive optical approaches in behaving animals. When combined with genetic and optogenetic techniques, the molecular mechanisms that modulate cell and circuit activity during different behavior states can be identified.
Here we describe methods for ratiometric Ca2+ imaging of single neurons in freely behaving Caenorhabditis elegans worms. We demonstrate a simple mounting technique that gently overlays worms growing on a standard Nematode Growth Media (NGM) agar block with a glass coverslip, permitting animals to be recorded at high-resolution during unrestricted movement and behavior. With this technique, we use the sensitive Ca2+ reporter GCaMP5 to record changes in intracellular Ca2+ in the serotonergic Hermaphrodite Specific Neurons (HSNs) as they drive egg-laying behavior. By co-expressing mCherry, a Ca2+-insensitive fluorescent protein, we can track the position of the HSN within ~ 1 &#181;m and correct for fluctuations in fluorescence caused by changes in focus or movement. Simultaneous, infrared brightfield imaging allows for behavior recording and animal tracking using a motorized stage. By integrating these microscopic techniques and data streams, we can record Ca2+ activity in the C. elegans egg-laying circuit as it progresses between inactive and active behavior states over tens of minutes.

Ratiometric Calcium Imaging of Individual Neurons in Behaving Caenorhabditis Elegans

This protocol describes the use of genetically encoded Ca2+ reporters to record changes in neural activity in behaving Caenorhabditis elegans worms. &#8195;

It has become increasingly clear that neural circuit activity in behaving animals differs substantially from that seen in anesthetized or immobilized ...

Imaging Dendritic Spines in Caenorhabditis elegans

Dendritic spines are specialized sites of synaptic innervation modulated by activity and serve as substrates for learning and memory. Recently, dendritic spines have been described for DD GABAergic neurons as the input sites from presynaptic cholinergic neurons in the motor circuit of Caenorhabditis elegans. This synaptic circuit can now serve as a powerful new in vivo model of spine morphogenesis and function that exploits the facile genetics and ready accessibility of C. elegans to live-cell imaging. 
This protocol describes experimental strategies for assessing DD spine structure and function. In this approach, a super-resolution imaging strategy is used to visualize the intricate shapes of actin-rich dendritic spines. To evaluate the DD spine function, the light-activated opsin, Chrimson, stimulates the presynaptic cholinergic neurons, and the calcium indicator, GCaMP, reports the evoked calcium transients in postsynaptic DD spines. Together, these methods comprise powerful approaches for identifying genetic determinants of dendritic spines in C. elegans that could also direct spine morphogenesis and function in the brain.

Imaging Dendritic Spines in Caenorhabditis elegans

Dendritic spines are important cellular features of the nervous system. Here live imaging methods are described for assessing the structure and function of dendritic spines in C. elegans.&#160;These approaches support the development of mutant screens for genes that define dendritic spine shape or function.

Dendritic spines are specialized sites of synaptic innervation modulated by activity and serve as substrates for learning and memory. Recently, dendritic ...