Name: activity of posterior lateral line afferent neurons during swimming in zebrafish
Uploaded: 2021-02-10T15:00:00
Description: Watch this Scientific Journal Video about Activity of Posterior Lateral Line Afferent Neurons during Swimming in Zebrafish at JoVE.com

We gratefully acknowledge support from the National Institute of Health (DC010809), National Science Foundation (IOS1257150, 1856237), and the Whitney Laboratory for Marine Biosciences to J.C.L.&#160;We would like to thank past and present members of the Liao Lab for stimulating discussions.

All animal care and experiments were performed in accordance with protocols approved by the University of Florida&#39;s Institutional Animal Care and Use Committee.
1. Preparation of materials for electrophysiological recordings
<ol>
	<li>Make a silicone elastomer-bottomed recording dish.
	<ol>
		<li>Dispense a thin layer of self-mixing silicone elastomer components (e.g., Sylgard) into a cover glass bottomed tissue culture dish until it levels with the rim of shallow well. Approximately 0.5...

The experimental protocol described provides the potential to monitor endogenous changes in sensory input across motor behaviors in an intact, behaving vertebrate. Specifically, it details an in vivo approach to performing simultaneous extracellular recordings of lateral line afferent neurons and ventral motor roots in larval zebrafish. Spontaneous afferent activity has been previously characterized in zebrafish without consideration of potential concurrent motor activity1,<sup class="x...

Afferent neurons of mechanosensory systems transmit information from hair cells to the brain during hearing and balance. Electrophysiology can reveal the sensitivity of afferent neurons through direct recordings. While whole cell patching from hair cells can be challenging, recording from downstream afferent neurons is easier and allows assessment of action potentials in response to controlled stimulations1,2,3. Stimulating hair cells lead to their deflection, which modifies mechanosensory structures, thus triggering an increase in action potentials (spikes) in afferent neurons4,5,6. In the absence of external stimuli, afferent neurons also spike spontaneously due to glutamate leak from the hair cells on to afferent post-synaptic terminals7,8, and have been shown to contribute toward maintaining sensitivity9,10. Patch clamp recording of afferent activity enables observation of hair cell sensitivity and signal dynamics that are not possible using techniques with lower temporal resolution, such as in microphonics11,12 or functional calcium imaging13,14,15. The following protocol will allow the recording of afferent activity concurrent with motor commands to reveal instantaneous changes in hair cell sensitivity.
Zebrafish (Danio rerio) use hair cells contained in neuromasts that compose the lateral line system to detect water movement relative to their body, which is translated into neural signals essential for navigation16,17,18, predator avoidance, prey capture19,20, and schooling21. Water flow can also be self-generated by the motions of swimming22,23,24, respiration22,25,26, and feeding27. These behaviors comprise repetitive movements that can fatigue hair cells and impair sensing. Therefore, it is critical that the lateral line system differentiates between external (exafferent) and self-generated (reafferent) flow stimuli. A corollary discharge attenuates self-generated flow signals during locomotion in zebrafish. This inhibitory predictive motor signal is relayed via descending neurons to the sensory receptors to modify the input or interrupt the processing of the reafferent feedback28,29. Seminal work contributing to our early understanding of this feedforward system relied on in vitro preparations where the connectivity and endogenous activity of the neural circuit were not maintained28,30,31,32,33,34,35. This protocol describes an approach to preserving an intact neural circuit where endogenous feedback dynamics are maintained thus enabling better understanding of the corollary discharge in vivo.
The protocol outlined here describes how to monitor posterior lateral line afferent neuron and motor neuron activity simultaneously in larval zebrafish. Characterizing afferent signal dynamics before, during, and after motor commands provides insights into real-time, endogenous feedback from the central nervous system that modulates hair cell sensitivity during locomotion. This protocol outlines what materials will need to be prepared prior to experiments and then describes how to paralyze and prepare zebrafish larvae. The protocol will describe how to establish a stable loose patch recording of afferent neurons and extracellular ventral root (VR) recordings of motor neurons. Representative data that can be obtained using this protocol are presented from an exemplar individual and analysis was performed on multiple replicates of the experimental protocol. Pre-processing of data is performed using custom written scripts in MATLAB. Overall, this in vivo experimental paradigm is poised to provide a better understanding of sensory feedback during locomotion in a model vertebrate hair cell system.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>100 mL beaker</td>
			<td>PYREX</td>
			<td>1000</td>
			<td>resceptacle for etchant</td>
		</tr>
		<tr>
			<td>10x water immersion objective</td>
			<td>Olympus</td>
			<td>UMPLFLN10xW</td>
			<td>low magnification for positioning larvae and recording electrode</td>
		</tr>
		<tr>
			<td>40x water immersion objective</td>
			<td>Olympus</td>
			<td>LUMPLFLN40XW</td>
			<td>higher magnification for position electrode tip and establishing patch-clamp</td>
		</tr>
		<tr>
			<td>abfload.m</td>
			<td></td>
			<td>supplemental coding file</td>
			<td>custom written MATLAB script for converting raw electrophysiology recordings to .mat files</td>
		</tr>
		<tr>
			<td>AffVR_preprocess.m</td>
			<td></td>
			<td>supplemental coding file</td>
			<td>custom written MATLAB script for preprocessing recording data</td>
		</tr>
		<tr>
			<td>BNC coaxial cables</td>
			<td>ThorLabs</td>
			<td>2249-C-12</td>
			<td>connecting amplifier and digitizer channels; require 4</td>
		</tr>
		<tr>
			<td>borosilicate glass capillaries w/ filament</td>
			<td>Warner Instruments</td>
			<td>G150F-3</td>
			<td>inner diameter: 0.86, outer diameter: 1.50; capillary glass used to form recording electrodes</td>
		</tr>
		<tr>
			<td>burst_detect</td>
			<td></td>
			<td>supplemental coding file</td>
			<td>custom written MATLAB function necessary to run AffVR_preprocess.m</td>
		</tr>
		<tr>
			<td>computer</td>
			<td>N/A</td>
			<td>N/A</td>
			<td>any computer should work</td>
		</tr>
		<tr>
			<td>DC Power Supply</td>
			<td>Tenma</td>
			<td>72-420</td>
			<td>used for electrically etching dissection pins</td>
		</tr>
		<tr>
			<td>electrophysiology digitizer</td>
			<td>Axon Instruments, Molecular Devices</td>
			<td>Axon DigiData 1440A</td>
			<td>enables acquisition of patch-clamp data</td>
		</tr>
		<tr>
			<td>filament</td>
			<td>Sutter Instrument Company</td>
			<td>FB255B</td>
			<td>2.5 mm box filament used in micropipette puller</td>
		</tr>
		<tr>
			<td>fine forceps</td>
			<td>Fine Science Tools</td>
			<td>Dumont #5 (0.05 x 0.02 mm) Item No. 11295-10</td>
			<td>used to manipulate larvae and insert pins</td>
		</tr>
		<tr>
			<td>fixed stage DIC microscope</td>
			<td>Olympus</td>
			<td>BX51WI</td>
			<td>microscope used to visualize and establish patch-clamp recordings</td>
		</tr>
		<tr>
			<td>flexible, tapered pipette tip</td>
			<td>Fisher Scientific</td>
			<td>02-707-169</td>
			<td>flexible tips enable insertion into recording electrode to dispense extracellular solution at the tip</td>
		</tr>
		<tr>
			<td>FluoroDish</td>
			<td>World Precision Instruments Inc.</td>
			<td>FD3510-100</td>
			<td>cover glass bottomed dish recording dish</td>
		</tr>
		<tr>
			<td>KimWipe</td>
			<td>KimTech</td>
			<td>34155</td>
			<td>task wipe used for wicking away excess fluid from larvae</td>
		</tr>
		<tr>
			<td>Kwik-Gard</td>
			<td>World Precision Instruments Inc.</td>
			<td>710172</td>
			<td>self-mixing sylgard elastomer</td>
		</tr>
		<tr>
			<td>MATLAB</td>
			<td>MathWorks</td>
			<td>R2020b</td>
			<td>command line software for preprocessing data</td>
		</tr>
		<tr>
			<td>microelectrode amplifier</td>
			<td>Axon Instruments, Molecular Devices</td>
			<td>MultiClamp 700B</td>
			<td>patch clamp amplifier for dual channel recordings</td>
		</tr>
		<tr>
			<td>microforge</td>
			<td>Narishige</td>
			<td>MF-830 microforge</td>
			<td>to polish recording electrode</td>
		</tr>
		<tr>
			<td>micromanipulator control unit</td>
			<td>Siskiyou</td>
			<td>MC1000-eR/T</td>
			<td>4-axis dial coordinator for controlling micromanipulator</td>
		</tr>
		<tr>
			<td>micropipette puller</td>
			<td>Sutter Instrument Company</td>
			<td>Flaming/Brown P-97</td>
			<td>for pulling capillary glass into recording electrodes</td>
		</tr>
		<tr>
			<td>microscope control unit</td>
			<td>Siskiyou</td>
			<td>MC1000e</td>
			<td>positions the microscope around the fixed stage and preparation</td>
		</tr>
		<tr>
			<td>motorized micromanipulator</td>
			<td>Siskiyou</td>
			<td>MX7600</td>
			<td>positions the headstage and attached recording electrode for patch-clamp recording</td>
		</tr>
		<tr>
			<td>MultiClamp Commander</td>
			<td>Molecular Devices</td>
			<td>2.2.2</td>
			<td>downloadable from Axon MultiClamp 700B Commander download page</td>
		</tr>
		<tr>
			<td>optical air table</td>
			<td>Newport Corporation</td>
			<td>VH3036W-OPT</td>
			<td>breadboard isolation table to float microscope and minimize vibrations during recordings</td>
		</tr>
		<tr>
			<td>pCLAMP</td>
			<td>Molecular Devices</td>
			<td>10.7.0</td>
			<td>downloadable from Axon pCLAMP 10 Electrophysiology Data Acquisition &#38; Analysis Software Download page</td>
		</tr>
		<tr>
			<td>permanent ink marker</td>
			<td>Sharpie</td>
			<td>order from amazon.com</td>
			<td>for marking the leading edge side of the VR electrode to ensure proper orientation when inserting into pipette holder</td>
		</tr>
		<tr>
			<td>petri-dish</td>
			<td>Falcon</td>
			<td>35-3001</td>
			<td>used to immerse larvae in paralytic</td>
		</tr>
		<tr>
			<td>pipette holder</td>
			<td>Molecular Devices</td>
			<td>1-HL-U</td>
			<td>hold recording electrode and connect to the headstage</td>
		</tr>
		<tr>
			<td>pneumatic transducer</td>
			<td>Fluke Biomedical Instruments</td>
			<td>DPM1B</td>
			<td>for controlling recording electrode internal pressure</td>
		</tr>
		<tr>
			<td>potassium hydroxide</td>
			<td>Sigma-Aldrich</td>
			<td>221473-25G</td>
			<td>etchant for etching dissection pins</td>
		</tr>
		<tr>
			<td>silicone tubing</td>
			<td>Tygon</td>
			<td>14-169-1A</td>
			<td>tubing to connect pneumatic transducer to pipette holder</td>
		</tr>
		<tr>
			<td>spike_detect</td>
			<td></td>
			<td>supplemental coding file</td>
			<td>custom written MATLAB function necessary to run AffVR_preprocess.m</td>
		</tr>
		<tr>
			<td>stereomicroscope</td>
			<td>Carl Zeiss</td>
			<td>Stemi 2000-C</td>
			<td>used to visualize pin tips and during preparation of larvae</td>
		</tr>
		<tr>
			<td>straight edge razor blade</td>
			<td>Canopus</td>
			<td>order from amazon.com</td>
			<td>cuts the tungsten wire while making dissection pins</td>
		</tr>
		<tr>
			<td>swimbout_detect</td>
			<td></td>
			<td>supplemental coding file</td>
			<td>custom written MATLAB function necessary to run AffVR_preprocess.m</td>
		</tr>
		<tr>
			<td>syringe</td>
			<td>Becton Dickinson Compoany</td>
			<td>309602</td>
			<td>filled with extracellular solution to inject into recording electrodes</td>
		</tr>
		<tr>
			<td>transfer pipette</td>
			<td>Sigma-Aldrich</td>
			<td>Z135003-500EA</td>
			<td>single use, non-sterile pipette for transfering larvae</td>
		</tr>
		<tr>
			<td>tricaine methanesulfonate</td>
			<td>Syndel</td>
			<td>12854</td>
			<td>pharmaceutical aneasthetic used to euthanize larvae with high dosage.</td>
		</tr>
		<tr>
			<td>tungsten wire</td>
			<td>World Precision Instruments Inc.</td>
			<td>715500</td>
			<td>0.002 inch, 50.8 &#956;m diameter; used to make dissection pins</td>
		</tr>
		<tr>
			<td>vacuum filtration unit</td>
			<td>Sigma-Aldrich</td>
			<td>SCGVU11RE</td>
			<td>single use, sterile, vacuum filtration units used to sterilize extracellular solution used for electrophysiology electrode ringer</td>
		</tr>
		<tr>
			<td>voltage-clamp current-clamp headstage</td>
			<td>Molecular Devices</td>
			<td>CV-7B</td>
			<td>supplied with MultiClamp 700B amplifier used as left and right headstages</td>
		</tr>
		<tr>
			<td>&#945;-bungarotoxin</td>
			<td>ThermoFisher</td>
			<td>B1601</td>
			<td>for immobilizing the larvae prior to recording</td>
		</tr>
	</tbody>
</table>

activity of posterior lateral line afferent neurons during swimming in zebrafish

Sensory systems gather cues essential for directing behavior, but animals must decipher what information is biologically relevant. Locomotion generates reafferent cues that animals must disentangle from relevant sensory cues of the surrounding environment. For example, when a fish swims, flow generated from body undulations is detected by the mechanoreceptive neuromasts, comprising hair cells, that compose the lateral line system. The hair cells then transmit fluid motion information from the sensor to the brain via the sensory afferent neurons. Concurrently, corollary discharge of the motor command is relayed to hair cells to prevent sensory overload. Accounting for the inhibitory effect of predictive motor signals during locomotion is, therefore, critical when evaluating the sensitivity of the lateral line system. We have developed an in vivo electrophysiological approach to simultaneously monitor posterior lateral line afferent neuron and ventral motor root activity in zebrafish larvae (4-7 days post fertilization) that can last for several hours. Extracellular recordings of afferent neurons are achieved using the loose patch clamp technique, which can detect activity from single or multiple neurons. Ventral root recordings are performed through the skin with glass electrodes to detect motor neuron activity. Our experimental protocol provides the potential to monitor endogenous or evoked changes in sensory input across motor behaviors in an intact, behaving vertebrate.

After zebrafish larvae are properly immobilized and the posterior lateral line afferent ganglion and VR recording is achieved, activity in both afferent and motor neurons can be measured simultaneously. Recording channels are displayed using gap-free recording protocols (step 1.4) for continuous monitoring of afferent and VR activity. In real-time, decreases in spontaneous afferent spike rate can be observed concurrent with VR activity indicative of fictive swim bouts (Figure 1E). We found t...

Watch this Scientific Journal Video about Activity of Posterior Lateral Line Afferent Neurons during Swimming in Zebrafish at JoVE.com

Activity of Posterior Lateral Line Afferent Neurons during Swimming in Zebrafish

We describe a protocol to monitor changes in the afferent neuron activity during motor commands in a model vertebrate hair cell system.

Sensory systems gather cues essential for directing behavior, but animals must decipher what information is biologically relevant. Locomotion generates ...

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