Name: functional analysis of the larval feeding circuit in drosophila
Uploaded: 2013-11-19T16:45:00
Description: Watch this Scientific Journal Video about Functional Analysis of the Larval Feeding Circuit in Drosophila at JoVE.com

The authors would like to acknowledge the President&#8217;s Research Fund from Saint Louis University awarded to W.S.N.

1. Maintenance of Population Cages
<ol>
	<li>Maintain population cages at 25 &#176;C on a 12 hr light-dark cycle. As long as the control and experimental groups are exposed to the same lighting conditions, then this technique can be performed in a standard laboratory setting.</li>
	<li>Allow females to lay eggs overnight on apple juice-agar plates.</li>
	<li>Collect newly hatched larvae by maintaining plates with newly deposited eggs at 25 &#176;C for 24 hr. Place a small dollop of yeast in the center of the plate to a...

<ol>
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Aberrant development of the serotonergic stomatogastric circuit, which occurs during late embryogenesis, will affect its mature function. Changes in the neurite architecture innervating the gut can be correlated with the functional output of the circuit, which is feeding rate (measured by mouth hook contractions in a yeast solution) (Figure 1). The use of the UAS-Gal4 bipartite system in Drosophila makes it possible to specifically target up- or down-regulated expression of a given transcript to...

Drosophila is an extremely powerful model system for studying neural circuit development due to rapid generation time, low experimental cost, and the ability to manipulate and control genetic and environmental factors. Neurogenesis, neuronal path finding and synaptogenesis are conserved between humans and Drosophila; therefore the mechanisms in creating, maintaining and modifying neural circuits are conserved as well.
Classical neurotransmitters, such as serotonin (5-hydroxytryptamine, or 5-HT) can serve as growth factors before adopting their roles as signaling molecules in the mature neural circuit1-3 Previous studies have shown that perturbed levels of 5-HT during embryogenesis alter the connectivity of mature neurons4. Others have shown that ectopic application of 5-HT to cultured Helisoma neurons repress neurite outgrowth as well as synaptogenesis5-7. In Drosophila, developmental 5-HT levels are inversely related to varicosity number and size, as well as the degree of aborization, along the length of neurites projecting to the foregut from the CNS8.
Serotonergic neurotransmission has been shown to modulate feeding behaviors in diverse species, including Drosophila8-9. The feeding circuit in Drosophila is a relatively simple circuit that can be used as a model to correlate the functional output (feeding) with alterations in the development of the axonal projections from the brain to the foregut. Schoofs et al. have shown that Drosophila larval feeding is regulated by central pattern generators that influence the musculature10. While the specific muscular anatomy is not completely understood, it has been shown that the antennal nerve, maxillary nerve, and prothoracic accessory nerve are responsible for the muscular targets involved in the feeding behavior. Most data involving the musculature and nerve anatomy of invertebrate feeding is limited to Calliphora larvae.
The feeding rate of second instar larvae can be assessed by retraction of the cephalopharyngeal sclerites (mouth hooks), and is reproducible and high-throughput. The cephalopharyngeal plates are innervated by fibers from central 5-HT neurons via the frontal nerve. The proventriculus, or foregut, is innervated by serotonergic fibers (recurrens nerve) that fasciculate in the midgut and are responsible for contractions of the foregut (Figure 1)11-12. Changes in axonal branching, and the number and size of varicosities along the neurite length, can be quantitated using immunohistochemical techniques. Manipulating neuronal 5-HT during development, either directly or indirectly, can change the functional output of this feeding circuit, which can be assessed and correlated with changes in the morphology of the neurite architecture.

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		<tr height="40">
			<td height="40" style="height:40px;width:217px;">Eclipse E-800 Microscope</td>
			<td style="width:175px;">Nikon Instruments</td>
			<td style="width:115px;"></td>
			<td style="width:251px;"></td>
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		<tr height="60">
			<td height="60" style="height:60px;width:217px;">Neuroleucida</td>
			<td style="width:175px;">MBF Biosciences</td>
			<td style="width:115px;">NL-15</td>
			<td style="width:251px;">Used to analyze gut fiber architecture, not necessary to have</td>
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		<tr height="20">
			<td height="20" style="height:20px;width:217px;">Northern Eclipse</td>
			<td style="width:175px;">Empix Inc</td>
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			<td style="width:251px;">Imaging software</td>
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		<tr height="60">
			<td height="60" style="height:60px;width:217px;">G-2E/C TRITC EX 528-553</td>
			<td style="width:175px;">Nikon Instruments</td>
			<td style="width:115px;">96312</td>
			<td style="width:251px;">Filter for specific secondary antibody</td>
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		<tr height="80">
			<td height="80" style="height:80px;width:217px;">N.A. 0.75; W.D. 0.72 mm; DIC Prism: 40xI, 40x I-C; Spring loaded</td>
			<td style="width:175px;">Nikon Instruments</td>
			<td style="width:115px;">MRH00400</td>
			<td style="width:251px;">Objective used for imaging</td>
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		<tr height="41">
			<td height="41" style="height:41px;width:217px;">Simple Neurite Tracer</td>
			<td style="width:175px;">NIH Image J</td>
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			<td style="width:251px;"><a href="http://fiji.sc/Simple_Neurite_Tracer">http://fiji.sc/Simple_Neurite_Tracer</a></td>
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functional analysis of the larval feeding circuit in drosophila

The serotonergic feeding circuit in Drosophila melanogaster larvae can be used to investigate neuronal substrates of critical importance during the development of the circuit. Using the functional output of the circuit, feeding, changes in the neuronal architecture of the stomatogastric system can be visualized. Feeding behavior can be recorded by observing the rate of retraction of the mouth hooks, which receive innervation from the brain. Locomotor behavior is used as a physiological control for feeding, since larvae use their mouth hooks to traverse across an agar substrate. Changes in feeding behavior can be correlated with the axonal architecture of the neurites innervating the gut. Using immunohistochemistry it is possible to visualize and quantitate these changes. Improper handling of the larvae during behavior paradigms can alter data as they are very sensitive to manipulations. Proper imaging of the neurite architecture innervating the gut is critical for precise quantitation of number and size of varicosities as well as the extent of branch nodes. Analysis of most circuits allow only for visualization of neurite architecture or behavioral effects; however, this model allows one to correlate the functional output of the circuit with the impairments in neuronal architecture.

The serotonergic feeding circuit in the Drosophila larva can serve as an extremely effective model to observe the influence of particular factors on nervous system development. By quantitating feeding rate, it is possible to link the axonal architecture of the feeding circuit with its functional output (Figure 1). The locomotor assay is used as a physiological control for the retractions of the mouth hooks, since larvae use their mouth hooks to propel themselves across the surface of the agar. T...

Watch this Scientific Journal Video about Functional Analysis of the Larval Feeding Circuit in Drosophila at JoVE.com

Functional Analysis of the Larval Feeding Circuit in Drosophila

The feeding circuit in Drosophila melanogaster larvae serves a simple yet powerful model that allows changes in feeding rate to be correlated with alterations in the stomatogastric neural circuitry. This circuit is composed of central serotonergic neurons that send projections to the mouth hooks as well as the foregut.

Functional Analysis of the Larval Feeding Circuit in Drosophila

The serotonergic  feeding circuit in Drosophila  melanogaster larvae can be used to investigate neuronal substrates of  critical importance during the ...

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