This work was supported by grants from the 973 Program (2014CB943002) and the National Natural Science Foundation of China (11534013, 31500841).

All experimental protocols involving animal subjects were approved by the Animal Ethics Committee of the Southern Medical University.
1. Prepare Solutions for Experiments
<ol>
	<li>Prepare the anesthetic (see Table of Materials): 1.5% pentobarbital sodium dissolved in ddH2O.</li>
	<li>Prepare the dissection solution (see Table of Materials): Dissolve one bag of Leiboviz&#39;s L-15 powder in 1 L of ddH2O. Adjust pH to 7.3 with 1 M NaOH. Adjust osmolarity to 300-330 mOsm by using an osmometer and 10 mM HEPES before use.</li>
	<li>Dissolve 2 mg/mL collagenase IV (see Table of Materials) in dissection solution prepared in step 1.2.</li>
	<li>Prepare the immunostaining solutions (see Table of Materials): Dissolve the 4% paraformaldehyde in phosphate buffered saline (PBS). 
	Caution: Paraformaldehyde is toxic; wear appropriate protection.</li>
	<li>Dilute the 0.3% permeability agent in PBS. Dilute the 10% normal goat serum in PBS as the blocking buffer. Dilute the prestin antibody 1:200 in blocking buffer. Dilute the Alexa488-conjugated antibody 1:600 in blocking buffer. Dilute the Phalloidin-Tetramethylrhodamine B isothiocyanate 1:200 in PBS.</li>
	<li>Prepare the extracellular solution (see Table of Materials): Prepare the Leiboviz&#39;s L-15 medium as described above (step 1.2).</li>
	<li>Prepare the intracellular solution (see Table of Materials).</li>
</ol>
2. ABR Recording
NOTE: ABR recording has been previously described in detail in our previous study9.
<ol>
	<li>Anesthetize Sprague Dawley (SD) rats (1-14 day old pups and 2-month old adults, both sexes) with a single injection of 1.5% sodium pentobarbital (22 mg/kg for pups and 30 mg/kg for adults, intraperitoneal (i.p.)).</li>
	<li>Place the anesthetized animal in a polyethylene-foam mold to immobilize the animal&#39;s body. Place the animal on an anti-vibration table in a sound-attenuating room. Keep the animal&#39;s body temperature at 37.5 &#176;C with a heating pad.</li>
	<li>Wipe the head area with 70% (vol/vol) ethanol. By using a fine scissors, make a 1-2 mm incision ventrolateral to the external pinna to place the reference electrode or ground. A subdermal needle electrode (recording electrode) is located over the skull vertex (Figure 1A).</li>
	<li>Using the function generator, generate calibrated tone bursts (1 ms rise/fall, 3 ms plateau) of various frequencies (2, 4, 8, 16, 24, and 32 kHz) and intensities (decreased from 85 to 10 dB SPL in 5 dB step). Vary the frequency and amplitude manually or using a computer. Deliver sound stimuli through an electrostatic speaker located 10 cm away toward the head of animal.</li>
	<li>Filter (100-1,000 Hz), amplify and average (256 times) the sound elicited potential using a multi-function processor to get the ABRs. The ABR traces is monitored online and stored for offline analysis. It takes about 40 min to complete the ABR recording from one animal. 
	NOTE: Usually, three to seven peaks (wave I to wave VII) with latencies less than 15 ms can be identified (Figure 1B). The ABR threshold is defined as the minimum sound level at which wave I and II could be detected.</li>
	<li>Euthanize before the animals awake from anesthesia (with an intraperitoneal injection of 0.3 mL 1.5% sodium pentobarbital).</li>
</ol>
3. The Organ of Corti (OC) Dissection
<ol>
	<li>Anesthetize rat pups. For rats less than 6 days old (&#60;P6), keep the animal in a 100 mm culture dish, and cover the dish with ice for 10 min. For rats &#62;P6, anesthetize the animal with a single injection of 1.5% sodium pentobarbital (22 mg/kg, i.p.). Decapitate the rat pups after anesthesia.</li>
	<li>Sterilize the head by spraying with 70% (vol/vol) ethanol.</li>
	<li>Open the skull along the sagittal midline with scissors; remove the brain to expose the inner ear.</li>
	<li>Transfer the inner ear into a 35-mm Petri dish filled with 3 mL of ice-cold L-15 (Figure 2A).</li>
	<li>Under the dissection microscope, use fine forceps to remove the bony capsule of the cochlea (Figure 2B).</li>
	<li>Unwrap the OC and associated stria vascularis (SV) from the modiolus.</li>
	<li>By holding the basal portion of the SV with forceps, separate the OC from the SV completely by unwinding slowly from base-to-apex (Figure 2C).</li>
	<li>Cut the OC evenly into three pieces by using fine scissors (Figure 2D).</li>
</ol>
4. Immunofluorescence Staining
<ol>
	<li>By using a 200 &#181;L pipette tip, transfer the segments of OC (step 3.8) onto a glass slide, and fix with 100 &#181;L of 4% paraformaldehyde for at least 4 h at 4 &#176;C. 
	Caution: Paraformaldehyde is toxic; wear appropriate protection.</li>
	<li>Wash the tissue by displacing the paraformaldehyde with 100 &#181;L of fresh PBS. Wash the tissue three times for 10 min.</li>
	<li>Incubate the tissue with 0.3% permeability agent in PBS for 30 min at room temperature.</li>
	<li>Discard the permeability agent in PBS and wash the tissue three times with PBS.</li>
	<li>Block with 10% normal goat serum in PBS for 1 h at room temperature.</li>
	<li>Incubate with anti-prestin-C-terminus antibody (1:200) in blocking solution for 2 h at room temperature or at 4 &#176;C overnight.</li>
	<li>Wash three times with PBS for 5 min.</li>
	<li>Incubate with Alexa488-conjugated secondary antibodies (1:600) in blocking solution for 1 h at room temperature in the dark.</li>
	<li>Wash three times with PBS for 5 min in the dark.</li>
	<li>Incubate with rhodamine-phalloidin (1:200) for 10 min at room temperature in the dark.</li>
	<li>Wash three times with PBS for 5 min in the dark.</li>
	<li>Mount on a glass slide with mounting medium (containing DAPI). Image with confocal microscopy by using 405 nm, 488 nm, and 594 nm lasers. Set the laser power at 0.1-0.5 mW and the scan speed at 0.5 frame/s.</li>
</ol>
5. Patch clamp Recording of Isolated OHCs
<ol>
	<li>Use the pipette puller and micro-forger to make patch pipettes with a tip diameter 2-3 &#181;m. Back-fill the pipettes with intracellular solution. Usually, the initial resistance of patch pipette was 2.5-3.5 M&#937; in bath solution.</li>
	<li>By using a 200 &#181;L pipette tip, transfer a piece of the OC (from step 3.8) into a 35 mm Petri dish. Digest the tissue with 100 &#181;L of enzymatic digestion medium (collagenase IV, see Table of Materials) for 5 min at room temperature.</li>
	<li>Displace the enzymatic digestion medium with 100 &#181;L of L-15. Cut the tissue into small pieces using a micro scalpel to isolate the hair cells.</li>
	<li>After gentle pipetting, transfer the cells into a homemade small plastic chamber (diameter ~ 1.5 cm) filled with enzyme-free bath solution (~ 1.5 mL, see Table of Materials).</li>
	<li>Place the chamber on the stage of an inverted microscope. Find the healthy-appearing solitary OHCs.</li>
	<li>Load the patch pipette into the head stage of a 700B amplifier. Move the patch pipette carefully by a micromanipulator and position it around the bottom of the outer hair cell (Figure 3A).</li>
	<li>Whole-cell patch clamp the OHC by sealing the lateral wall of the cell body. Apply light suction until the cell membrane is ruptured. Set the holding potential at -70 mV. Cells with access resistance ranged from 10 to 17 M&#937; and membrane resistance ranged from 100 to 500 M&#937;, and are considered a successful whole-cell configuration.</li>
	<li>Using computer control, apply hyperpolarizing and depolarizing voltage (250 ms duration and ranging from &#8722;140 to +94 mV in 13 mV steps) to the cell to elicit whole-cell currents.</li>
	<li>Amplify the whole-cell currents, filter (corner frequency of 5 kHz) by a 700B amplifier. Convert the data by a 1440A converter and store for offline analysis.</li>
	<li>Measure the membrane capacitance of OHCs using a two sine-wave voltage stimulus protocol controlled by a patch clamp software. Set the stimulate voltage range from -140 to 110 mV. Store the data for offline analysis.</li>
</ol>

<ol>
	<li>He, D. Z., Zheng, J., Kalinec, F., Sacchi Kakehata, S. S. a. n. t. o. s. -., J, <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tuning+in+to+the+amazing+outer+hair+cell:+membrane+wizardry+with+a+twist+and+shout.">Tuning in to the amazing outer hair cell: membrane wizardry with a twist and shout.</a> J Membr Biol. 209, 119-134 (2006).</li><li>Dallos, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cochlear+amplification,+outer+hair+cells+and+prestin.">Cochlear amplification, outer hair cells and prestin.</a> Curr Opin Neurobiol. 18, 370-376 (2008).</li><li>Zheng, J., 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=Prestin+is+the+motor+protein+of+cochlear+outer+hair+cells.">Prestin is the motor protein of cochlear outer hair cells.</a> Nature. 405, 149-155 (2000).</li><li>Abe, 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=Developmental+expression+of+the+outer+hair+cell+motor+prestin+in+the+mouse.">Developmental expression of the outer hair cell motor prestin in the mouse.</a> J Membr Biol. 215, 49-56 (2007).</li><li>Waguespack, J., Salles, F. T., Kachar, B., Ricci, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stepwise+morphological+and+functional+maturation+of+mechanotransduction+in+rat+outer+hair+cells.">Stepwise morphological and functional maturation of mechanotransduction in rat outer hair cells.</a> J Neurosci. 27, 13890-13902 (2007).</li><li>Zhang, L. I., Bao, S., Merzenich, M. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Persistent+and+specific+influences+of+early+acoustic+environments+on+primary+auditory+cortex.">Persistent and specific influences of early acoustic environments on primary auditory cortex.</a> Nat Neurosci. 4, 1123 (2001).</li><li>De, V. -. S. E., Chang, E. F., Bao, S., Merzenich, M. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Critical+period+window+for+spectral+tuning+defined+in+the+primary+auditory+cortex+(A1)+in+the+rat.">Critical period window for spectral tuning defined in the primary auditory cortex (A1) in the rat.</a> J Neurosci. 27, 180-189 (2007).</li><li>He, D. Z., Evans, B. N., Dallos, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=First+appearance+and+development+of+electromotility+in+neonatal+gerbil+outer+hair+cells.">First appearance and development of electromotility in neonatal gerbil outer hair cells.</a> Hearing Res. 78, 77-90 (1994).</li><li>Hang, J., 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=Synchronized+Progression+of+Prestin+Expression+and+Auditory+Brainstem+Response+during+Postnatal+Development+in+Rats.">Synchronized Progression of Prestin Expression and Auditory Brainstem Response during Postnatal Development in Rats.</a> Neural Plast. , 4545826 (2016).</li><li>Ehret, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+absolute+auditory+thresholds+in+the+house+mouse+(Mus+musculus).">Development of absolute auditory thresholds in the house mouse (Mus musculus).</a> J Am Audiol Soc. 1, 179-184 (1976).</li><li>M&#248;ller, A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Hearing:anatomy, physiology, and disorders of the auditory system. , (2006).</li><li>He, D. Z., Zheng, J., Edge, R., Dallos, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+of+cochlear+inner+hair+cells.">Isolation of cochlear inner hair cells.</a> Hearing Res. 145, 156-160 (2000).</li><li>Tang, J., Pecka, J. L., Tan, X., Beisel, K. W., He, D. Z. Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Engineered+Pendrin+Protein,+an+Anion+Transporter+and+Molecular+Motor.">Engineered Pendrin Protein, an Anion Transporter and Molecular Motor.</a> J Biological Chem. 286, 31014-31021 (2011).</li><li>Fu, M., 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=The+Effects+of+Urethane+on+Rat+Outer+Hair+Cells.">The Effects of Urethane on Rat Outer Hair Cells.</a> Neural Plast. 2016, 1-11 (2016).</li></ol>

The authors have nothing to disclose.

In rats younger than day 11, no action potential in response to sound stimulation could be observed in auditory cortex6,7. Therefore, postnatal day 11 is described as &#34;hearing onset&#34;10. The development of hearing function before hearing onset was not well studied yet. Using the similar method for adult ABR recording, we demonstrate that ABRs could be elicited by pure tone burst from rat pups younger than P11 (F...

Two distinct functions of cochlear sensory hair cells are essential for mammalian hearing: mechanoelectric transduction (MET) and electromotility1,2. By MET channels located in the hair bundle, IHCs (IHCs) and OHCs convert sound vibration into membrane potential changes, as well as the electrical signals of innervated spiral ganglion neurons. OHCs change their cell length with the membrane potential and amplify the vibration of low-level sound. This activity termed electromotility is derived by the motor protein prestin located in the lateral wall of OHCs3.
In many species including rodents, the hearing function is immature in early postnatal epoch4,5. No action potential in response to sound signals could be detected in the auditory cortex before the hearing onset6,7. Development of morphology and function of the cochlea has been widely studied in mouse, gerbil, and rat4,5,8. The mechanotransduction and electromotility of hair cells are also developed in the early life epoch5.
In order to evaluate the hearing sensitivity of rats at different postnatal ages, we have developed a method for auditory brainstem response (ABR) recording in rat pups. Whole-cell patch clamp is an ideal technology to investigate the OHCs electrophysiologically. However, compared with the patch clamp performed in neurons and other epithelial cells, the low rate of whole-cell sealing limited the investigation of electromotility of isolated OHCs.
Here we describe a procedure to investigate the OHCs morphologically and electrophysiologically in acutely dissociated cochlea from postnatal rats. This method can be modified to study the molecular mechanisms that regulate inner hair cell development and function.

<table>
	<tbody>
		<tr>
			<td>Anesthetic</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Pentobarbital sodium</td>
			<td>Sigma</td>
			<td>P3761</td>
			<td>1.5% in water</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Dissection solution</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Leiboviz&#39;s L-15 Medium</td>
			<td>Life Technologies</td>
			<td>41300-039</td>
			<td>1 pack in 1 L water</td>
		</tr>
		<tr>
			<td>Collagenase IV</td>
			<td>Sigma</td>
			<td>C5138</td>
			<td>2 mg/mL in L-15</td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td>Sigma</td>
			<td>7365-45-9</td>
			<td>10 mM</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Immunostaining solutions</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>Thermo Fisher Scientific</td>
			<td>10010023</td>
			<td>PH 7.3</td>
		</tr>
		<tr>
			<td>Paraformaldehyde</td>
			<td>Sigma</td>
			<td>158127</td>
			<td>4% in PBS</td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>Amresco</td>
			<td>ZS-0694</td>
			<td>0.3% in PBS</td>
		</tr>
		<tr>
			<td>Normal goat serum</td>
			<td>Thermo Fisher Scientific</td>
			<td>10000C</td>
			<td>10% in PBS</td>
		</tr>
		<tr>
			<td>prestin antibody</td>
			<td>Santa Cruz</td>
			<td>SC-22694</td>
			<td>dil 1:200</td>
		</tr>
		<tr>
			<td>Alexa Fluor 488-conjugated antibody</td>
			<td>Thermo Fisher Scientific</td>
			<td>A-11055</td>
			<td>dil 1:600</td>
		</tr>
		<tr>
			<td>Phalloidin-Tetramethylrhodamine B isothiocyanate</td>
			<td>Sigma</td>
			<td>P1951</td>
			<td>dil 1:200</td>
		</tr>
		<tr>
			<td>DAPI</td>
			<td>Solarbio</td>
			<td>C0060</td>
			<td>dil 1:20</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Extracellular solution</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Leiboviz&#39;s L-15 Medium</td>
			<td>Life Technologies</td>
			<td>41300-039</td>
			<td>1 pack in 1 L water</td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td>Sigma</td>
			<td>7365-45-9</td>
			<td>10 mM</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Intracellular solution</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>CsCl</td>
			<td>Sigma</td>
			<td>7647-17-8</td>
			<td>140 mM</td>
		</tr>
		<tr>
			<td>MgCl2</td>
			<td>Sigma</td>
			<td>7791-18-6</td>
			<td>2 mM</td>
		</tr>
		<tr>
			<td>EGTA</td>
			<td>Sigma</td>
			<td>67-42-5</td>
			<td>10 mM</td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td>Sigma</td>
			<td>7365-45-9</td>
			<td>10 mM</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Osmometer</td>
			<td>Gonotec</td>
			<td>OSMOMAT 3000 basic</td>
			<td></td>
		</tr>
		<tr>
			<td>Forcep</td>
			<td>WPI</td>
			<td>14095</td>
			<td>Tweezers dumont</td>
		</tr>
		<tr>
			<td>Micropipette puller</td>
			<td>Sutter Instrument</td>
			<td>MODLE-P97</td>
			<td></td>
		</tr>
		<tr>
			<td>Micro Forge</td>
			<td>Narishigen</td>
			<td>MF-830</td>
			<td></td>
		</tr>
		<tr>
			<td>Mini Operating System</td>
			<td>Sutter Instrument</td>
			<td>MP-285</td>
			<td></td>
		</tr>
		<tr>
			<td>MultiClamp</td>
			<td>Axon</td>
			<td>700B</td>
			<td></td>
		</tr>
		<tr>
			<td>Low-Noise Data Acquisition System</td>
			<td>Axon</td>
			<td>1440A</td>
			<td></td>
		</tr>
		<tr>
			<td>ES1 speaker</td>
			<td>Tucker-Davis Technologies</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>TDT system 3</td>
			<td>Tucker-Davis Technologies</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Software</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>SigGenRP software</td>
			<td>Tucker-Davis Technologies</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>BioSigRP software</td>
			<td>Tucker-Davis Technologies</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>jClamp</td>
			<td>Scientific Solutions</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Animal</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>SD rat</td>
			<td>Experimental Animal Center of Southern Medical University</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

auditory brainstem response and outer hair cell whole-cell patch clamp recording in postnatal rats

The outer hair cell is one of the two types of sensory hair cells in the mammalian cochlea. They alter their cell length with the receptor potential to amplify the weak vibration of low-level sound signal. The morphology and electrophysiological property of outer hair cells (OHCs) develop in early postnatal ages. The maturation of outer hair cell may contribute to the development of the auditory system. However, the process of OHCs development is not well studied. This is partly because of the difficulty to measure their function by an electrophysiological approach. With the purpose of developing a simple method to address the above issue, here we describe a step-by-step protocol to study the function of OHCs in acutely dissociated cochlea from postnatal rats. With this method, we can evaluate the cochlear response to pure tone stimuli and examine the expression level and function of the motor protein prestin in OHCs. This method can also be used to investigate the inner hair cells (IHCs).

ABR can be elicited from anesthetized rat pups older than postnatal day 7 (P7) using pure tone bursts (Figure 1A). As shown in Figure 1B, the ABR waveforms obtained from rat pups showed only three to four distinct waves with small amplitude. Usually, up to seven peaks were observed in the ABR waveforms of adult animals (Figure 1B).
For the ...

Watch this Scientific Journal Video about Auditory Brainstem Response and Outer Hair Cell Whole-cell Patch Clamp Recording in Postnatal Rats at JoVE.com

Auditory Brainstem Response and Outer Hair Cell Whole-cell Patch Clamp Recording in Postnatal Rats

This protocol describes methods to record the auditory brainstem response from postnatal rat pups. To examine the functional development of outer hair cells, the experimental procedure of whole-cell patch clamp recording in isolated outer hair cells is described step-by-step.

The outer hair cell is one of the two types of sensory hair cells in the mammalian cochlea. They alter their cell length with the receptor potential to ...

auditory-brainstem-response-outer-hair-cell-whole-cell-patch-clamp

Research

JoVE Journal

Neuroscience

9.4K Views.  Southern Medical University. This protocol describes methods to record the auditory brainstem response from postnatal rat pups. To examine the functional development of outer hair cells, the experimental procedure of whole-cell patch clamp recording in isolated outer hair cells is described step-by-step.

Video: Auditory Brainstem Response and Outer Hair Cell Whole-cell Patch Clamp Recording in Postnatal Rats

Preparation and Culture of Chicken Auditory Brainstem Slices

The chicken auditory brainstem is a well-established model system that has been widely used to study the anatomy and physiology of auditory processing at discreet periods of development 1-4 as well as mechanisms for temporal coding in the central nervous system 5-7.
Here we present a method to prepare chicken auditory brainstem slices that can be used for acute experimental procedures or to culture organotypic slices for long-term experimental manipulations.
The chicken auditory brainstem is composed of nucleus angularis, magnocellularis, laminaris and superior olive. These nuclei are responsible for binaural sound processing and single coronal slice preparations preserve the entire circuitry. Ultimately, organotypic slice cultures can provide the opportunity to manipulate several developmental parameters such as synaptic activity, expression of pre and postsynaptic components, expression of aspects controlling excitability and differential gene expression
This approach can be used to broaden general knowledge about neural circuit development, refinement and maturation.

The chicken auditory brainstem is comprised of nuclei responsible for binaural sound processing. A single coronal slice preparation maintains the entire circuitry while the cultured approach provides a unique preparation to study the development of neuronal structure and auditory function at the molecular, cellular and network levels.

The chicken auditory brainstem is a well-established model system that has been widely used to study the anatomy and physiology of auditory processing at ...

Patch Clamp Recordings in Inner Ear Hair Cells Isolated from Zebrafish

Patch clamp analyses of the voltage-gated channels in sensory hair cells isolated from a variety of species have been described previously1-4 but this video represents the first application of those techniques to hair cells from zebrafish. Here we demonstrate a method to isolate healthy, intact hair cells from all of the inner ear end-organs: saccule, lagena, utricle and semicircular canals. Further, we demonstrate the diversity in hair cell size and morphology and give an example of the kinds of patch clamp recordings that can be obtained. The advantage of the use of this zebrafish model system over others stems from the availability of zebrafish mutants that affect both hearing and balance. In combination with the use of transgenic lines and other techniques that utilize genetic analysis and manipulation, the cell isolation and electrophysiological methods introduced here should facilitate greater insight into the roles hair cells play in mediating these sensory modalities.

The purpose of this video is to demonstrate procedures for obtaining healthy, intact hair cells from the inner ear organs of adult zebrafish and then using them for patch clamp studies aimed at characterizing the biophysical properties of their voltage-gated channels.

Patch  clamp analyses of the voltage-gated channels in sensory hair cells isolated  from a variety of species have been described previously1-4 but this  ...

Whole Cell Patch Clamp for Investigating the Mechanisms of Infrared Neural Stimulation

It has been demonstrated in recent years that pulsed, infrared laser light can be used to elicit electrical responses in neural tissue, independent of any further modification of the target tissue. Infrared neural stimulation has been reported in a variety of peripheral and sensory neural tissue in vivo, with particular interest shown in stimulation of neurons in the auditory nerve. However, while INS has been shown to work in these settings, the mechanism (or mechanisms) by which infrared light causes neural excitation is currently not well understood. The protocol presented here describes a whole cell patch clamp method designed to facilitate the investigation of infrared neural stimulation in cultured primary auditory neurons. By thoroughly characterizing the response of these cells to infrared laser illumination in vitro under controlled conditions, it may be possible to gain an improved understanding of the fundamental physical and biochemical processes underlying infrared neural stimulation.

Infrared nerve stimulation has been proposed as an alternative to electrical stimulation in a range of nerve types, including those associated with the auditory system. This protocol describes a patch clamp method for studying the mechanism of infrared nerve stimulation in a culture of primary auditory neurons.

It has been  demonstrated in recent years that pulsed, infrared laser light can be used to  elicit electrical responses in neural tissue, independent of ...

Whole-cell Patch-clamp Recordings from Morphologically- and Neurochemically-identified Hippocampal Interneurons

GABAergic inhibitory interneurons play a central role within neuronal circuits of the brain. Interneurons comprise a small subset of the neuronal population (10-20%), but show a high level of physiological, morphological, and neurochemical heterogeneity, reflecting their diverse functions. Therefore, investigation of interneurons provides important insights into the organization principles and function of neuronal circuits. This, however, requires an integrated physiological and neuroanatomical approach for the selection and identification of individual interneuron types. Whole-cell patch-clamp recording from acute brain slices of transgenic animals, expressing fluorescent proteins under the promoters of interneuron-specific markers, provides an efficient method to target and electrophysiologically characterize intrinsic and synaptic properties of specific interneuron types. Combined with intracellular dye labeling, this approach can be extended with post-hoc morphological and immunocytochemical analysis, enabling systematic identification of recorded neurons. These methods can be tailored to suit a broad range of scientific questions regarding functional properties of diverse types of cortical neurons.

Cortical networks are controlled by a small, but diverse set of inhibitory interneurons. Functional investigation of interneurons therefore requires targeted recording and rigorous identification. Described here is a combined approach involving whole-cell recordings from single or synaptically-coupled pairs of neurons with intracellular labeling, post-hoc morphological and immunocytochemical analysis.

GABAergic inhibitory interneurons play a central role within neuronal circuits of the brain. Interneurons comprise a small subset of the neuronal ...

Recording Light-evoked Postsynaptic Responses in Neurons in Dark-adapted, Mouse Retinal Slice Preparations Using Patch Clamp Techniques

The retina is the gateway to the visual system. To understand visual signal processing mechanisms, we investigate retinal neural network functions. Retinal neurons in the network comprise of numerous subtypes. More than 10 subtypes of bipolar cells, ganglion cells, and amacrine cells have been identified by morphological studies. Multiple subtypes of retinal neurons are thought to encode distinct features of visual signaling, such as motion and color, and form multiple neural pathways. However, the functional roles of each neuron in visual signal processing are not fully understood. The patch clamp method is useful to address this fundamental question. Here, a protocol to record light-evoked synaptic responses in mouse retinal neurons using patch clamp recordings in dark-adapted conditions is provided. The mouse eyes are dark-adapted O/N, and retinal slice preparations are dissected in a dark room using infrared illumination and viewers. Infrared light does not activate mouse photoreceptors and thus preserves their light responsiveness. Patch clamp is used to record light-evoked responses in retinal neurons. A fluorescent dye is injected during recordings to characterize neuronal morphological subtypes. This procedure enables us to determine the physiological functions of each neuron in the mouse retina.

We will demonstrate how to prepare retinal slices from the mouse eye and record light responses in retinal neurons. The entire procedure is conducted in dark-adapted conditions.

The retina is the gateway to the visual system. To understand visual signal processing mechanisms, we investigate retinal neural network functions. ...

Whole-cell Patch-clamp Recordings in Brain Slices

Whole-cell patch-clamp recording is an electrophysiological technique that allows the study of the&#160;electrical properties of a substantial part of the neuron. In this configuration, the micropipette is in tight contact with the cell membrane, which prevents current leakage and thereby provides more accurate ionic current measurements than the previously used intracellular sharp electrode recording method. Classically, whole-cell recording can be performed on neurons in various types of preparations, including cell culture models, dissociated neurons, neurons in brain slices, and in intact anesthetized or awake animals. In summary, this technique has immensely contributed to the understanding of passive and active biophysical properties of excitable cells. A major advantage of this technique is that it provides information on how specific manipulations (e.g., pharmacological, experimenter-induced plasticity) may alter specific neuronal functions or channels in real-time. Additionally, significant opening of the plasma membrane allows the internal pipette solution to freely diffuse into the cytoplasm, providing means for introducing drugs, e.g., agonists or antagonists of specific intracellular proteins, and manipulating these targets without altering their functions in neighboring cells. This article will focus on whole-cell recording performed on neurons in brain slices,&#160;a preparation that has the advantage of recording neurons in relatively well preserved brain circuits, i.e., in a physiologically relevant context. In particular,&#160;when combined with appropriate pharmacology, this technique is a powerful tool allowing identification of specific neuroadaptations that occurred following any type of experiences, such as learning, exposure to drugs of abuse, and stress. In summary, whole-cell patch-clamp recordings in brain slices provide means to measure in ex vivo preparation long-lasting changes in neuronal functions that have developed in intact awake animals.

This protocol describes basic procedural steps for performing whole-cell patch-clamp recordings. This technique allows the study of&#160;the electrical behavior of neurons, and when performed in brain slices, allows the assessment of various neuronal functions from neurons that are still integrated in relatively well preserved brain circuits.

Whole-cell patch-clamp recording is an electrophysiological technique that allows the study of the&#160;electrical properties of a substantial part of the ...

Whole-cell Patch-clamp Recordings for Electrophysiological Determination of Ion Selectivity in Channelrhodopsins

Over the past decade, channelrhodopsins became indispensable in neuroscientific research where they are used as tools to non-invasively manipulate electrical processes in target cells. In this context, ion selectivity of a channelrhodopsin is of particular importance. This article describes the investigation of chloride selectivity for a recently identified anion-conducting channelrhodopsin of Proteomonas sulcata via electrophysiological patch-clamp recordings on HEK293 cells. The experimental procedure for measuring light-gated photocurrents demands a fast switchable &#8211; ideally monochromatic &#8211; light source coupled into the microscope of an otherwise conventional patch-clamp setup. Preparative procedures prior to the experiment are outlined involving preparation of buffered solutions, considerations on liquid junction potentials, seeding and transfection of cells, and pulling of patch pipettes. The actual recording of current-voltage relations to determine the reversal potentials for different chloride concentrations takes place 24 h to 48 h after transfection. Finally, electrophysiological data are analyzed with respect to theoretical considerations of chloride conduction.

This article describes how the ion selectivity of channelrhodopsin is determined with electrophysiological whole-cell patch-clamp recordings using HEK293 cells. Here, the experimental procedure for investigating chloride selectivity of an anion-selective channelrhodopsin is demonstrated. However, the procedure is transferable to other channelrhodopsins of distinct selectivity.

Over the past decade, channelrhodopsins became indispensable in neuroscientific research where they are used as tools to non-invasively manipulate ...

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

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

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

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

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

Preparations and Protocols for Whole Cell Patch Clamp Recording of Xenopus laevis Tectal Neurons

The Xenopus tadpole retinotectal circuit, comprised of the retinal ganglion cells (RGCs) in the eye which form synapses directly onto neurons in the optic tectum, is a popular model to study how neural circuits self-assemble. The ability to carry out whole cell patch clamp recordings from tectal neurons and to record RGC-evoked responses, either in vivo or using a whole brain preparation, has generated a large body of high-resolution data about the mechanisms underlying normal, and abnormal, circuit formation and function. Here we describe how to perform the in vivo preparation, the original whole brain preparation, and a more recently developed horizontal brain slice preparation for obtaining whole cell patch clamp recordings from tectal neurons. Each preparation has unique experimental advantages. The in vivo preparation enables the recording of the direct response of tectal neurons to visual stimuli projected onto the eye. The whole brain preparation allows for the RGC axons to be activated in a highly controlled manner, and the horizontal brain slice preparation allows recording from across all layers of the tectum.

Preparations and Protocols for Whole Cell Patch Clamp Recording of Xenopus laevis Tectal Neurons

In this paper, we discuss three brain preparations used for whole cell patch clamp recording to study the retinotectal circuit of Xenopus laevis tadpoles. Each preparation, with its own specific advantages, contributes to the experimental tractability of the Xenopus tadpole as a model to study neural circuit function.

The Xenopus tadpole retinotectal circuit, comprised of the retinal ganglion cells (RGCs) in the eye which form synapses directly onto neurons in the optic ...

Cochlear Implant Surgery and Electrically-evoked Auditory Brainstem Response Recordings in C57BL/6 Mice

Cochlear implants (CIs) are neuroprosthetic devices that can provide a sense of hearing to deaf people. However, a CI cannot restore all aspects of hearing. Improvement of the implant technology is needed if CI users are to perceive music and perform in more natural environments, such as hearing out a voice with competing talkers, reflections, and other sounds. Such improvement requires experimental animals to better understand the mechanisms of electric stimulation in the cochlea and its responses in the whole auditory system. The mouse is an increasingly attractive model due to the many genetic models available. However, the limited use of this species as a CI model is mainly due to the difficulty of implanting small electrode arrays. More details about the surgical procedure are therefore of great interest to expand the use of mice in CI research.
In this report, we describe in detail the protocol for acute deafening and cochlear implantation of an electrode array in the C57BL/6 mouse strain. We demonstrate the functional efficacy of this procedure with electrically-evoked auditory brainstem response (eABR) and show examples of facial nerve stimulation. Finally, we also discuss the importance of including a deafening procedure when using a normally hearing animal. This mouse model provides a powerful opportunity to study genetic and neurobiological mechanisms that would be of relevance for CI users.

Animal models of cochlear implants can advance knowledge of the technological bases of treating permanent sensorineural hearing loss with electrical stimulation. This study presents a surgical protocol for acute deafening and cochlear implantation of an electrode array in mice as well as the functional assessment with auditory brainstem response.

Cochlear implants (CIs) are neuroprosthetic devices that can provide a sense of hearing to deaf people. However, a CI cannot restore all aspects of ...