Funding for this work was provided by a Garnett Passe and Rodney Williams Memorial Foundation Project grant to R. Lim and A.J. Camp.

1. Animals
<ol>
	<li>Mice were obtained from the Australian Rodent Centre (ARC; Perth, Australia) and held at the University of Sydney Bosch Animal Facility on a normal 12-hr light/dark cycle with environmental enrichment. All experiments described were approved by The University of Sydney Animal Ethics Committee.</li>
	<li>Male and female mice (C57/Bl6) were used for all experiments since this strain are commonly used as the background for genetic manipulation, and can be considered equivalent to wildtype 8-9.</li>
</ol>
2. Tissue Preparation
<ol>
	<li>Prepare 300 ml of a glycerol-based artificial cerebrospinal fluid (ACSF) consisting of (in mM): 26 NaHCO3, 11 glucose, 250 glycerol, 2.5 KCl, 1.2 NaH2PO4, 1.2 MgCl2, and 2.5 CaCl2. Prior to the addition of CaCl2, gas the solution with carbogen (95% O2 and 5% CO2) to establish a pH of 7.4 and avoid calcium precipitation (cloudiness). Freeze the solution in a -80 &deg;C freezer for 45 min so that an ice slurry is formed.</li>
	<li>Deeply anaesthetize mice with ketamine (100 mg/kg) (Parnell, Alexandria, Australia) via an intra-peritoneal injection.</li>
	<li>Once hind-limb pinch reflexes are absent decapitate mice using sharp stainless steel scissors and make a sagittal skin incision using a razor blade (rounded #22) to expose the skull. At this point and throughout steps 2.3-2.8 the cranial vault, brain, and underlying vestibular apparatus should be kept as cool as possible by regular application of ice-cold ACSF over the tissue.</li>
	<li>Using the pointed arm of standard pattern scissors (FST, North Vancouver, Canada) make a small incision in the skull at Lambda and cut along the sagittal suture. Ensure that the brain is not "dragged" by the shear blade during this step.</li>
	<li>Carefully peel the parietal bones away laterally and the occipital bone posteriorly using shallow bend pearson rongeurs (FST).</li>
	<li>A small stainless steel spatula is then used to gently lift the brain from the surface of the middle and posterior cranial fossae, and the exposed vestibulocochlea nerve (CNVIII) cut midway between the inner ear and the brainstem with a pair of fine iris scissors. Cutting this nerve minimizes undue tension on axons of the primary afferents and their connections with hair cells.</li>
	<li>Following transection of CN VIII the brain is removed in toto.</li>
	<li>The vestibular labyrinth is now clearly visible in the middle cranial fossa, with the cochlea pointing anteromedially. Rongeur either side of the vestibular labyrinth before gently excising by gripping the anterior semicircular canal and pulling laterally.</li>
	<li>Immerse the excised labyrinths (Figure 1) in a dissecting dish containing the ice-cold, continuously gassed ACSF described in section 2.1. Under a stereomicroscope, hold the labyrinth to the base of the dish by gripping the cochlea. Use fine forceps to scratch away at the bone overlying the anterior semicircular canal ampulla. Once a small hole in the bone is achieved begin to flick the bone away from the ampulla. Caution should be taken not to push the forceps through the bone as this can cause damage to the underlying membranous labyrinth and sensory epithelium. Continue this procedure until both the anterior and adjacent horizontal semicircular membranous ducts and ampullae are exposed (Figure 2).</li>
</ol>
<img alt="Figure 1" src="/files/ftp_upload/50471/50471fig1.jpg" /> 
Figure 1. The isolated mouse vestibular labyrinth. A. Left panel) Schematic representation of the isolated mouse vestibular labyrinth. Important points of reference for accessing the vestibular sensory epithelium, the cochlea, anterior, and horizontal semicircular canals are labeled. Asterisks indicate the semicircular canal ampulla containing the vestibular sensory epithelium. B. Right panel) Photomicrograph of the isolated vestibular labyrinth from a 1-month-old mouse.
<img alt="Figure 2" src="/files/ftp_upload/50471/50471fig2.jpg" /> 
Figure 2. Exposure of the Membranous vestibular labyrinth. The bone overlying the anterior and horizontal semicircular canal ampullae have been scratched away to reveal the black/brown-speckled membranous ampullae and associated ampullary nerves (CNVIII). The schematic in the bottom panel represents the structures in the highlighted region of the photomicrograph and shows the relationship of the semicircular canal ducts to the ampullae and CNVIII.
<ol start="10">
	<li>Using fine forceps, gently lift the ampullae and associated utricle away from the bony labyrinth, ensuring that the central region of the ampullae (containing the sensory epithelium) is not damaged. In some cases the proximal part of the semicircular membranous duct may need to be cut with iris scissors to release the ampullae from the bone.</li>
	<li>Transfer the triad containing the two ampullae and utricle into a Petri dish filled with Leibovitz's L-15 culture medium (Sigma-Aldrich, St. Louis, MO). Use a fiber optic to "backlight" the tissue. This allows clear visualization of the crista containing the sensory epithelium within the ampullae.</li>
	<li>Carefully make an incision in the speckled "roof" of the utricle with the fine iris scissors. Continue this incision through the roof of the anterior and then the horizontal ampullae. Make the incision as close to the edge of the sensory epithelium as possible without contacting it (Figure 3A). Ensure that there are no pieces of membrane overlying the sensory epithelium (Figure 3B).</li>
	<li>Transfer the isolated semi intact preparation to a small glass-bottomed recording chamber filled with L-15 media. Weigh down the preparation using a grid of fine nylon fibers secured to a flattened U-shaped platinum wire (Figure 3B). Ideally, the fibers of the grid should not overlie the sensory epithelium, however in some cases where more stability is required, a single fiber transecting the sensory epithelium maybe preferred.</li>
</ol>
<img alt="Figure 3" src="/files/ftp_upload/50471/50471fig3.jpg" /> 
Figure 3. The isolated semi-intact preparation of the vestibular sensory epithelium. A. Schematic representation of the semi-intact preparation and electrode configuration. The ampulla overlying the crista has been "de-roofed" to expose the surface of the sensory epithelium (green). B. Photomicrograph of the semi-intact 'triad' preparation showing the anterior (ac) and horizontal (hc) crista (utricle obscured behind ac). Note the nylon fiber used to secure the preparation to the base of the recording chamber. Scale bar: 100 &mu;m. C. A recording electrode positioned on an individual vestibular hair cell. Scale bar: 15 &mu;m.
3. Electrophysiology
<ol>
	<li>Perfuse the semi-intact preparation with continuously oxygenated L-15 medium. The media contains a pH indicator (phenol red) and color of the medium should be monitored throughout the recordings. The pH with oxygen should be 7.3-7.4 and correspond to a red color.</li>
	<li>Prepare recording pipettes from 1.5 mm (1.19 mm ID) borosilicate glass using a two-step protocol (heat step 1: 72; and heat step 2: 50) on a micropipette puller (Narishige, Japan, model PP-830) to achieve a final impedance of 3-4 M&Omega;.</li>
	<li>Fill the shank of the pipette with 3-4 mm of Potassium fluoride-based internal solution containing (in mM) 110 KF, 12 KCl, 27 KOH, 1 NaCl, 10 HEPES, 10 EGTA, 1.8 MgCl2, 3 D-glucose, and 2 Na-ATP; pH 7.4 with KOH.</li>
	<li>Wrap the shank of the pipette 2-3 times and as far down to the tip as possible with a thin strip of parafilm to insulate the electrode and reduce pipette capacitance.</li>
	<li>Position the pipette over the sensory epithelium under low power magnification (5X) on an upright microscope (Olympus BX51). Switch to high power (40X) and visualize individual vestibular hair cells with an attached CCD camera.</li>
	<li>Position pipette on the membrane of a visualized hair cell (Figure 3C) using a micromanipulator (Sutter Instruments, California, USA). Once a gigaohm seal is achieved, rupture the cell membrane with a small amount of negative pressure applied through a suction port on the pipette holder.</li>
	<li>Make whole-cell voltage clamp recordings using standard techniques 8-9.</li>
</ol>
4. Two-photon Microscopy
<ol>
	<li>Prepare a 0.9% saline solution containing 5 mM Oregon Green 488 BAPTA-1 (OGB-1; hexapotassium salt; Invitrogen, Germany).</li>
	<li>While still submerged, place the "de-roofed" semi-intact triad preparation onto a small piece of filter paper (4X4 mm, 0.8 &mu;m thick; Millipore, Germany) ensuring that the sensory epithelium is unobstructed from above.</li>
	<li>Transfer the filter paper and preparation onto the saline covered base platinum electrode (7 &mu;l) of an electroporator consisting of the combination of a pulse generator and a wide-band amplifier, and cover with a further 5 &mu;l of 5 mM solution of the synthetic calcium indicator dye Oregon Green 488 BAPTA-1 (Figure 4).</li>
</ol>
<img alt="Figure 4" src="/files/ftp_upload/50471/50471fig4.jpg" /> 
Figure 4. Bulk electroporation. A. schematic showing cross-section of electroporation configuration. The semi-intact preparation (*) is placed on a piece of filter paper immersed in calcium dye (Oregon Green 488 BAPTA-1) and current applied between 2 platinum electrodes. Adapted from Briggman and Euler, 2011 10.
<ol start="4">
	<li>Bring the top platinum electrode parallel with the base electrode at a distance of approximately 2 mm, being careful not to disrupt the orientation of the preparation when contact with the Oregon Green 488 BAPTA-1 solution is made.</li>
	<li>Pass a brief current pulse across the preparation (Parameters for the current; +13 V, 10 msec pulse width, 1 Hz frequency, 10 square-wave pulses) 10-11.</li>
	<li>On the bottom of a glass bottomed recording chamber filled with L-15 medium, place a small dab of silicon oil and position the semi-intact preparation onto it, again ensuring that the sensory epithelium is unobstructed from above. To ensure stability throughout imaging, replace the nylon grid over the preparation as described above (see point 2.13).</li>
	<li>Using the two-photon microscope make optical recordings of spontaneous calcium activity in the sensory epithelium (Figure 7) using standard imaging protocols 10-11.</li>
</ol>

<ol>
	<li>Dulon, D., Safieddine, S., Jones, S. M., Petit, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Otoferlin+is+critical+for+a+highly+sensitive+and+linear+calcium-dependent+exocytosis+at+vestibular+hair+cell+ribbon+synapses.">Otoferlin is critical for a highly sensitive and linear calcium-dependent exocytosis at vestibular hair cell ribbon synapses.</a> J. Neurosci. 29, 10474-10487 (2009).</li><li>Highstein, S., Art, J., Holstein, G., Rabbitt, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simultaneous+pre-+and+post-synaptic+recording+from+the+peripheral+vestibular+calyx+and+its+included+type+I+hair+cell.">Simultaneous pre- and post-synaptic recording from the peripheral vestibular calyx and its included type I hair cell.</a> , (2009).</li><li>Kindig, A. E., Lim, R., Callister, R. J., Brichta, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Voltage+dependent+currents+in+type+I+and+II+hair+cell+and+calyx+terminals+of+primary+afferents+in+an+intact+in+vitro+mouse+vestibular+crista+preparation.">Voltage dependent currents in type I and II hair cell and calyx terminals of primary afferents in an intact in vitro mouse vestibular crista preparation.</a> , (2009).</li><li>Chatlani, S., Goldberg, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Whole-cell+recordings+from+calyx+endings+in+the+turtle+posterior+crista.">Whole-cell recordings from calyx endings in the turtle posterior crista.</a> , (2010).</li><li>Songer, J. E., Eatock, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transduction+in+the+mammalian+saccule.">Transduction in the mammalian saccule.</a> , (2010).</li><li>Lee, H. Y., Camp, A. J., Callister, R. J., Brichta, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vestibular+primary+afferent+activity+in+an+in+vitro+preparation+of+the+mouse+inner+ear.">Vestibular primary afferent activity in an in vitro preparation of the mouse inner ear.</a> J. Neurosci. Methods. 145, 73-87 (2005).</li><li>Lim, R., Kindig, A. E., Donne, S. W., Callister, R. J., Brichta, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Potassium+accumulation+between+type+I+hair+cells+and+calyx+terminals+in+mouse+crista.">Potassium accumulation between type I hair cells and calyx terminals in mouse crista.</a> Exp. Brain Res. 210, 607-621 (2011).</li><li>Camp, A. J., Callister, R. J., Brichta, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inhibitory+synaptic+transmission+differs+in+mouse+type+A+and+B+medial+vestibular+nucleus+neurons+in+vitro.">Inhibitory synaptic transmission differs in mouse type A and B medial vestibular nucleus neurons in vitro.</a> J. Neurophysiol. 95, 3208-3218 (2006).</li><li>Camp, A. 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=Attenuated+glycine+receptor+function+reduces+excitability+of+mouse+medial+vestibular+nucleus+neurons.">Attenuated glycine receptor function reduces excitability of mouse medial vestibular nucleus neurons.</a> Neuroscience. 170, 348-360 (2010).</li><li>Briggman, K. L., Euler, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bulk+electroporation+and+population+calcium+imaging+in+the+adult+mammalian+retina.">Bulk electroporation and population calcium imaging in the adult mammalian retina.</a> J. Neurophysiol. 105, 2601-2609 (2011).</li><li>Briggman, K. L., Helmstaedter, M., Denk, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Wiring+specificity+in+the+direction-selectivity+circuit+of+the+retina.">Wiring specificity in the direction-selectivity circuit of the retina.</a> Nature. 471, 183-188 (2011).</li><li>Rennie, K. J., Streeter, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Voltage-dependent+currents+in+isolated+vestibular+afferent+calyx+terminals.">Voltage-dependent currents in isolated vestibular afferent calyx terminals.</a> J. Neurophysiol. 95, 26-32 (2006).</li><li>Hudspeth, A. J., Lewis, R. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Kinetic+analysis+of+voltage-+and+ion-dependent+conductances+in+saccular+hair+cells+of+the+bull-frog,+Rana+catesbeiana.">Kinetic analysis of voltage- and ion-dependent conductances in saccular hair cells of the bull-frog, Rana catesbeiana.</a> J. Physiol. 400, 237-274 (1988).</li><li>Rennie, K. J., Ashmore, J. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ionic+currents+in+isolated+vestibular+hair+cells+from+the+guinea-pig+crista+ampullaris.">Ionic currents in isolated vestibular hair cells from the guinea-pig crista ampullaris.</a> Hear. Res. 51, 279-291 (1991).</li></ol>

The authors declare that they have no competing financial interests.

The mechanisms underlying our sense of balance have received limited attention in comparison with other sensory systems, e.g. the visual and auditory systems. Of the studies that have investigated changes in vestibular or balance function, most have focused on behavioral measures including the vestibulo-ocular reflex, with incomplete knowledge of the fundamental building blocks of balance- the vestibular hair cells themselves. Those studies that have concentrated on the hair cells have almost invariably do...

Despite the significant contribution of the vestibular system to our everyday lives, a clear understanding of the processes responsible for the observed decline in vestibular function with age remain elusive. One reason for this lack of knowledge is that decline in vestibular function has almost exclusively been explored using behavioral assays, including the vestibulo-ocular reflex (VOR), a precise indicator of extrinsic vestibular function, but provides limited insights into the changes of intrinsic components. This is a major impediment to our understanding of vestibular hair cell function in health, disease, or aging.
While there have been many studies of individual vestibular hair cells, a major shortcoming has been the reliance on acute hair cell preparations, where hair cells and even calyx afferent terminals are removed from their normal environment via mechanical and/or enzymatic treatment. Such approaches inevitably disrupt the delicate microarchitecture between hair cell and calyx, and hair cell and supporting cell. With the development of semi-intact preparations 1-5, and an isolated mouse labyrinth preparation 6, there is now an opportunity to study the various forms of synaptic communication under conditions that more closely resemble those in vivo. Indeed, Lim et al. (2011) showed marked differences in whole cell currents recorded from acutely isolated type I vestibular hair cells compared to those that remained embedded within the neuroepithelium. Specifically, potassium is thought to accumulate in the intercellular space, between the hair cell and calyx afferent, and significantly alter hair cell response7. This type of information would be impossible to obtain without the semi-intact preparation of the vestibular sensory epithelium described here. We demonstrate the semi-intact preparation of the mouse crista 3, and show representative results obtained from whole-cell patch electrophysiology, and two-photon calcium imaging.

<table border="1">
 <tbody>
 <tr>
 <td></td>
 <td></td>
 <td></td>
 <td>REAGENTS</td>
 </tr>
 <tr>
 <td>Leibovitz medium L-15</td>
 <td>Sigma Aldrich</td>
 <td>L4386-10X1L</td>
 <td></td>
 </tr>
 <tr>
 <td>BAPTA-1-oregon green</td>
 <td>Invitrogen</td>
 <td>O6806 </td>
 <td></td>
 </tr>
 <tr>
 <td></td>
 <td></td>
 <td></td>
 <td>EQUIPMENT </td>
 </tr>
 <tr>
 <td>Stereo microscope</td>
 <td>Leica Microsystems</td>
 <td>A60S</td>
 <td></td>
 </tr>
 <tr>
 <td>Upright microscope</td>
 <td>Olympus</td>
 <td>BX51WI</td>
 <td></td>
 </tr>
 <tr>
 <td>Two-photon microscope</td>
 <td>Olympus/La Vision</td>
 <td>BX51WI/ TriMScope II</td>
 <td></td>
 </tr>
 <tr>
 <td>Dumont #5 SF Forceps</td>
 <td>FST</td>
 <td>11252-00</td>
 <td></td>
 </tr>
 <tr>
 <td>Friedman-Pearson Rongeurs</td>
 <td>FST</td>
 <td>16221-14</td>
 <td></td>
 </tr>
 <tr>
 <td>Standard Pattern Scissors</td>
 <td>FST</td>
 <td>14001-12</td>
 <td></td>
 </tr>
 <tr>
 <td>InstraTECH A-D converter</td>
 <td>HEKA</td>
 <td>ITC-18</td>
 <td></td>
 </tr>
 <tr>
 <td>Sutter Micromanipulator</td>
 <td>Sutter</td>
 <td>MP-225/M</td>
 <td></td>
 </tr>
 <tr>
 <td>multiclamp amplifier</td>
 <td>Axon Instruments</td>
 <td>700B</td>
 <td></td>
 </tr>
 <tr>
 <td>Data acquisition software (electrophysiology)</td>
 <td>Axograph</td>
 <td>N/A</td>
 <td></td>
 </tr>
 <tr>
 <td>Imspector Data acquisition software (two-photon)</td>
 <td>Max Planck innovation</td>
 <td>N/A</td>
 <td></td>
 </tr>
 </tbody>
</table>

an isolated semi-intact preparation of the mouse vestibular sensory epithelium for electrophysiology and high-resolution two-photon microscopy

Understanding vestibular hair cells function under normal conditions, or how trauma, disease, and aging disrupt this function is a vital step in the development of preventative approaches and/or novel therapeutic strategies. However, the majority of studies looking at abnormal vestibular function have not been at the cellular level but focused primarily on behavioral assays of vestibular dysfunction such as gait analyses and vestibulo-ocular reflex performance. While this work has yielded valuable data about what happens when things go wrong, little information is gleaned regarding the underlying causes of dysfunction. Of the studies that focus on the cellular and subcellular processes that underlie vestibular function, most have relied on acutely isolated hair cells, devoid of their synaptic connections and supporting cell environment. Therefore, a major technical challenge has been access to the exquisitely sensitive vestibular hair cells in a preparation that is least disrupted, physiologically. Here we demonstrate a semi-intact preparation of the mouse vestibular sensory epithelium that retains the local micro-environment including hair cell/primary afferent complexes.

The electrophysiological properties of vestibular hair cells are dependent on the complex microarchitecture within which they are embedded 7. Figure 5 shows that the semi-intact vestibular epithelium preparation can be used to differentiate between type I hair cells (Figure 5A), type II hair cells (Figure 5B), and the calyx primary afferent (Figure 5C) based on characteristic whole cell conductances. These characteristics include a prono...

Watch this Scientific Journal Video about An Isolated Semi-intact Preparation of the Mouse Vestibular Sensory Epithelium for Electrophysiology and High-resolution Two-photon Microscopy at JoVE.com

An Isolated Semi-intact Preparation of the Mouse Vestibular Sensory Epithelium for Electrophysiology and High-resolution Two-photon Microscopy

Analysis of vestibular hair cell function is complicated by their location deep within the hardest part of the skull, the petrous temporal bone. Most functional hair cell studies have used acutely isolated hair cells. Here we describe a semi-intact preparation of mouse vestibular epithelium for electrophysiological and two-photon microscopy studies.

Understanding vestibular hair cells function  under normal conditions, or how trauma, disease, and aging disrupt this  function is a vital step in the ...

an-isolated-semi-intact-preparation-mouse-vestibular-sensory

Research

JoVE Journal

Neuroscience

11.8K Views.  University of Sydney. Analysis of vestibular hair cell function is complicated by their location deep within the hardest part of the skull, the petrous temporal bone. Most functional hair cell studies have used acutely isolated hair cells. Here we describe a semi-intact preparation of mouse vestibular epithelium for electrophysiological and two-photon microscopy studies.

Video: An Isolated Semi-intact Preparation of the Mouse Vestibular Sensory Epithelium for Electrophysiology and High-resolution Two-photon Microscopy

In vivo Imaging of the Mouse Spinal Cord Using Two-photon Microscopy

In vivo imaging using two-photon microscopy 1 in mice that have been genetically engineered to express fluorescent proteins in specific cell types 2-3 has significantly broadened our knowledge of physiological and pathological processes in numerous tissues in vivo 4-7. In studies of the central nervous system (CNS), there has been a broad application of in vivo imaging in the brain, which has produced a plethora of novel and often unexpected findings about the behavior of cells such as neurons, astrocytes, microglia, under physiological or pathological conditions 8-17. However, mostly technical complications have limited the implementation of in vivo imaging in studies of the living mouse spinal cord. In particular, the anatomical proximity of the spinal cord to the lungs and heart generates significant movement artifact that makes imaging the living spinal cord a challenging task.
We developed a novel method that overcomes the inherent limitations of spinal cord imaging by stabilizing the spinal column, reducing respiratory-induced movements and thereby facilitating the use of two-photon microscopy to image the mouse spinal cord in vivo. This is achieved by combining a customized spinal stabilization device with a method of deep anesthesia, resulting in a significant reduction of respiratory-induced movements. This video protocol shows how to expose a small area of the living spinal cord that can be maintained under stable physiological conditions over extended periods of time by keeping tissue injury and bleeding to a minimum. Representative raw images acquired in vivo detail in high resolution the close relationship between microglia and the vasculature. A timelapse sequence shows the dynamic behavior of microglial processes in the living mouse spinal cord. Moreover, a continuous scan of the same z-frame demonstrates the outstanding stability that this method can achieve to generate stacks of images and/or timelapse movies that do not require image alignment post-acquisition. Finally, we show how this method can be used to revisit and reimage the same area of the spinal cord at later timepoints, allowing for longitudinal studies of ongoing physiological or pathological processes in vivo.

In vivo Imaging of the Mouse Spinal Cord Using Two-photon Microscopy

A minimally invasive protocol to stabilize the mouse spinal column and perform repetitive in vivo spinal cord imaging using two-photon microscopy is described. This method combines a spinal stabilization device and an anesthetic regimen to minimize respiratory-induced movements and produce raw imaging data that require no alignment or other post-processing.

In vivo imaging using two-photon microscopy 1 in mice that have been genetically engineered to express fluorescent proteins in specific cell types 2-3 has ...

Tissue Preparation and Immunostaining of Mouse Sensory Nerve Fibers Innervating Skin and Limb Bones

Detection and primary processing of physical, chemical and thermal sensory stimuli by peripheral sensory nerve fibers is key to sensory perception in animals and humans. These peripheral sensory nerve fibers express a plethora of receptors and ion channel proteins which detect and initiate specific sensory stimuli. Methods are available to characterize the electrical properties of peripheral sensory nerve fibers innervating the skin, which can also be utilized to identify the functional expression of specific ion channel proteins in these fibers. However, similar electrophysiological methods are not available (and are also difficult to develop) for the detection of the functional expression of receptors and ion channel proteins in peripheral sensory nerve fibers innervating other visceral organs, including the most challenging tissues such as bone. Moreover, such electrophysiological methods cannot be utilized to determine the expression of non-excitable proteins in peripheral sensory nerve fibers. Therefore, immunostaining of peripheral/visceral tissue samples for sensory nerve fivers provides the best possible way to determine the expression of specific proteins of interest in these nerve fibers. So far, most of the protein expression studies in sensory neurons have utilized immunostaining procedures in sensory ganglia, where the information is limited to the expression of specific proteins in the cell body of specific types or subsets of sensory neurons. Here we report detailed methods/protocols for the preparation of peripheral/visceral tissue samples for immunostaining of peripheral sensory nerve fibers. We specifically detail methods for the preparation of skin or plantar punch biopsy and bone (femur) sections from mice for immunostaining of peripheral sensory nerve fibers. These methods are not only key to the qualitative determination of protein expression in peripheral sensory neurons, but also provide a quantitative assay method for determining changes in protein expression levels in specific types or subsets of sensory fibers, as well as for determining the morphological and/or anatomical changes in the number and density of sensory fibers during various pathological states. Further, these methods are not confined to the staining of only sensory nerve fibers, but can also be used for staining any types of nerve fibers in the skin, bones and other visceral tissue.

Immunocytochemical identification of peripheral sensory nerve fiber subtypes (and detection of protein expression therein) are key to the understanding of molecular mechanisms underlying peripheral sensation. Here we describe methods for preparation of peripheral/visceral tissue samples, such as skin and limb bones, for specific immunostaining of peripheral sensory nerve fibers.

Detection and primary processing of physical, chemical and thermal sensory stimuli by peripheral sensory nerve fibers is key to sensory perception in ...

An In-vitro Preparation of Isolated Enteric Neurons and Glia from the Myenteric Plexus of the Adult Mouse

The enteric nervous system is a vast network of neurons and glia running the length of the gastrointestinal tract that functionally controls gastrointestinal motility. A procedure for the isolation and culture of a mixed population of neurons and glia from the myenteric plexus is described. The primary cultures can be maintained for over 7 days, with connections developing among the neurons and glia. The longitudinal muscle strip with the attached myenteric plexus is stripped from the underlying circular muscle of the mouse ileum or colon and subjected to enzymatic digestion. In sterile conditions, the isolated neuronal and glia population are preserved within the pellet following centrifugation and plated on coverslips. Within 24-48 hr, neurite outgrowth occurs and neurons can be identified by pan-neuronal markers. After two days in culture, isolated neurons fire action potentials as observed by patch clamp studies. Furthermore, enteric glia can also be identified by GFAP staining. A network of neurons and glia in close apposition forms within 5 - 7 days. Enteric neurons can be individually and directly studied using methods such as immunohistochemistry, electrophysiology, calcium imaging, and single-cell PCR. Furthermore, this procedure can be performed in genetically modified animals. This methodology is simple to perform and inexpensive. Overall, this protocol exposes the components of the enteric nervous system in an easily manipulated manner so that we may better discover the functionality of the ENS in normal and disease states.

An In-vitro Preparation of Isolated Enteric Neurons and Glia from the Myenteric Plexus of the Adult Mouse

We demonstrate a cell culture protocol for the direct study of neuronal and glial components of the enteric nervous system. A neuron/glia mixed culture on coverslips is prepared from the myenteric plexus of adult mouse providing the ability to examine individual neuron and glia function by electrophysiology, immunohistochemical, etc.

The enteric nervous system is a vast network of neurons and glia running the length of the gastrointestinal tract that functionally controls ...

Two-Photon in vivo Imaging of Dendritic Spines in the Mouse Cortex Using a Thinned-skull Preparation

In the mammalian cortex, neurons form extremely complicated networks and exchange information at synapses. Changes in synaptic strength, as well as addition/removal of synapses, occur in an experience-dependent manner, providing the structural foundation of neuronal plasticity. As postsynaptic components of the most excitatory synapses in the cortex, dendritic spines are considered to be a good proxy of synapses. Taking advantages of mouse genetics and fluorescent labeling techniques, individual neurons and their synaptic structures can be labeled in the intact brain. Here we introduce a transcranial imaging protocol using two-photon laser scanning microscopy to follow fluorescently labeled postsynaptic dendritic spines over time in vivo. This protocol utilizes a thinned-skull preparation, which keeps the skull intact and avoids inflammatory effects caused by exposure of the meninges and the cortex. Therefore, images can be acquired immediately after surgery is performed. The experimental procedure can be performed repetitively over various time intervals ranging from hours to years. The application of this preparation can also be expanded to investigate different cortical regions and layers, as well as other cell types, under physiological and pathological conditions.

Two-Photon in vivo Imaging of Dendritic Spines in the Mouse Cortex Using a Thinned-skull Preparation

Time-lapse imaging in the living animal provides valuable information on structural reorganization in the intact brain. Here, we introduce a thinned-skull preparation that allows transcranial imaging of fluorescently labeled synaptic structures in the living mouse cortex by two-photon microscopy.

In the mammalian cortex, neurons form extremely complicated networks and exchange information at synapses. Changes in synaptic strength, as well as ...

Two-photon Imaging of Cellular Dynamics in the Mouse Spinal Cord

Two-photon (2P) microscopy is utilized to reveal cellular dynamics and interactions deep within living, intact tissues. Here, we present a method for live-cell imaging in the murine spinal cord. This technique is uniquely suited to analyze neural precursor cell (NPC) dynamics following transplantation into spinal cords undergoing neuroinflammatory demyelinating disorders. NPCs migrate to sites of axonal damage, proliferate, differentiate into oligodendrocytes, and participate in direct remyelination. NPCs are thereby a promising therapeutic treatment to ameliorate chronic demyelinating diseases. Because transplanted NPCs migrate to the damaged areas on the ventral side of the spinal cord, traditional intravital 2P imaging is impossible, and only information on static interactions was previously available using histochemical staining approaches. Although this method was generated to image transplanted NPCs in the ventral spinal cord, it can be applied to numerous studies of transplanted and endogenous cells throughout the entire spinal cord. In this article, we demonstrate the preparation and imaging of a spinal cord with enhanced yellow fluorescent protein-expressing axons and enhanced green fluorescent protein-expressing transplanted NPCs.

A new ex vivo preparation for imaging the mouse spinal cord. This protocol allows for two-photon imaging of live cellular interactions throughout the spinal cord.

Two-photon (2P) microscopy is utilized to reveal cellular dynamics and interactions deep within living, intact tissues. Here, we present a method for ...

Quantification of Cerebral Vascular Architecture using Two-photon Microscopy in a Mouse Model of HIV-induced Neuroinflammation

Human Immunodeficiency Virus 1 (HIV-1) infection frequently results in HIV-1 Associated Neurocognitive Disorders (HAND), and is characterized by a chronic neuroinflammatory state within the central nervous system (CNS), thought to be driven principally by virally-mediated activation of microglia and brain resident macrophages. HIV-1 infection is also accompanied by changes in cerebrovascular blood flow (CBF), raising the possibility that HIV-associated chronic neuroinflammation may lead to changes in CBF and/or in cerebral vascular architecture. To address this question, we have used a mouse model for HIV-induced neuroinflammation, and we have tested whether long-term exposure to this inflammatory environment may damage brain vasculature and result in rarefaction of capillary networks. In this paper we describe a method to quantify changes in cortical capillary density in a mouse model of neuroinflammatory disease (HIV-1 Tat transgenic mice). This generalizable approach employs in vivo two-photon imaging of cortical capillaries through a thin-skull cortical window, as well as ex vivo two-photon imaging of cortical capillaries in mouse brain sections. These procedures produce images and z-stack files of capillary networks, respectively, which can be then subjected to quantitative analysis in order to assess changes in cerebral vascular architecture.

This paper describes a method by which the vascular architecture in the brain can be quantified using in vivo and ex vivo two-photon microscopy.

Human Immunodeficiency Virus 1 (HIV-1) infection frequently results in HIV-1 Associated Neurocognitive Disorders (HAND), and is characterized by a chronic ...

Physiological Preparation of Hair Cells from the Sacculus of the American Bullfrog (Rana catesbeiana)

The study of hearing and balance rests upon insights drawn from biophysical studies of model systems. One such model, the sacculus of the American bullfrog, has become a mainstay of auditory and vestibular research. Studies of this organ have revealed how sensory cells hair can actively detect signals from the environment. Because of these studies, we now better understand the mechanical gating and localization of a hair cell&#39;s transduction channels, calcium&#39;s role in mechanical adaptation, and the identity of hair cell currents. This highly accessible organ continues to provide insight into the workings of hair cells. Here we describe the preparation of the bullfrog&#39;s sacculus for biophysical studies on its hair cells. We include the complete dissection procedure and provide specific protocols for the preparation of the sacculus in specific contexts. We additionally include representative results using this preparation, including the calculation of a hair bundle&#39;s instantaneous force-displacement relation and measurement of a bundle&#39;s spontaneous oscillation.

Physiological Preparation of Hair Cells from the Sacculus of the American Bullfrog Rana catesbeiana

The American bullfrog&#39;s (Rana catesbeiana) sacculus permits direct examination of hair-cell physiology. Here the dissection and preparation of the bullfrog&#39;s sacculus for biophysical studies is described. We show representative experiments from these hair cells, including the calculation of a bundle&#39;s force-displacement relation and measurement of its unforced motion.

The study of hearing and balance rests upon insights drawn from biophysical studies of model systems. One such model, the sacculus of the American ...

In Vivo Two-photon Imaging of Cortical Neurons in Neonatal Mice

Two-photon imaging is a powerful tool for the in vivo analysis of neuronal circuits in the mammalian brain. However, a limited number of in vivo imaging methods exist for examining the brain tissue of live newborn mammals. Herein we summarize a protocol for imaging individual cortical neurons in living neonatal mice. This protocol includes the following two methodologies: (1) the Supernova system for sparse and bright labeling of cortical neurons in the developing brain, and (2) a surgical procedure for the fragile neonatal skull. This protocol allows the observation of temporal changes of individual cortical neurites during neonatal stages with a high signal-to-noise ratio. Labeled cell-specific gene silencing and knockout can also be achieved by combining the Supernova with RNA interference and CRISPR/Cas9 gene editing systems. This protocol can, thus, be used for analyzing the developmental dynamics of cortical neurons, molecular mechanisms that control the neuronal dynamics, and changes in neuronal dynamics in disease models.

In Vivo Two-photon Imaging of Cortical Neurons in Neonatal Mice

We present an in vivo two-photon imaging protocol for imaging the cerebral cortex of neonatal mice. This method is suitable for analyzing the developmental dynamics of cortical neurons, the molecular mechanisms that control the neuronal dynamics, and the changes in neuronal dynamics in disease models.

Two-photon imaging is a powerful tool for the in vivo analysis of neuronal circuits in the mammalian brain. However, a limited number of in vivo imaging ...

Transpupillary Two-Photon In Vivo Imaging of the Mouse Retina

The retina transforms light signals from the environment into electrical signals that are propagated to the brain. Diseases of the retina are prevalent and cause visual impairment and blindness. Understanding how such diseases progress is critical to formulating new treatments. In vivo&#160;microscopy in animal models of disease is a powerful tool for understanding neurodegeneration and has led to important progress towards treatments of conditions ranging from Alzheimer&#39;s disease to stroke. Given that the retina is the only central nervous system structure inherently accessible by optical approaches, it naturally lends itself towards in vivo imaging. However, the native optics of the lens and cornea present some challenges for effective imaging access.
This protocol outlines methods for in vivo two-photon imaging of cellular cohorts and structures in the mouse retina at cellular resolution, applicable for both acute- and chronic-duration imaging experiments. It presents examples of retinal ganglion cell (RGC), amacrine cell, microglial, and vascular imaging using a suite of labeling techniques including adeno-associated virus (AAV) vectors, transgenic mice, and inorganic dyes. Importantly, these techniques extend to all cell types of the retina, and suggested methods for accessing other cellular populations of interest are described. Also detailed are example strategies for manual image postprocessing for display and quantification. These techniques are directly applicable to studies of retinal function in health and disease.

In vivo imaging is a powerful tool for the study of biology in health and disease. This protocol describes transpupillary imaging of the mouse retina with a standard two-photon microscope. It also demonstrates different in vivoimaging methods to fluorescently label multiple cellular cohorts of the retina.

The retina transforms light signals from the environment into electrical signals that are propagated to the brain. Diseases of the retina are prevalent ...

In Vivo Chronic Two-Photon Imaging of Microglia in the Mouse Hippocampus

Microglia, the only immune cells resident in the brain, actively participate in neural circuit maintenance by modifying synapses and neuronal excitability. Recent studies have revealed the differential gene expression and functional heterogeneity of microglia in different brain regions. The unique functions of the hippocampal neural network in learning and memory may be associated with the active roles of microglia in synapse remodeling. However, inflammatory responses induced by surgical procedures have been problematic in the two-photon microscopic analysis of hippocampal microglia. Here, a method is presented that enables the chronic observation of microglia in all layers of the hippocampal CA1 through an imaging window. This method allows the analysis of morphological changes in microglial processes for more than 1 month. Long-term and high-resolution imaging of the resting microglia requires minimally invasive surgical procedures, appropriate objective lens selection, and optimized imaging techniques. The transient inflammatory response of hippocampal microglia may prevent imaging immediately after surgery, but the microglia restore their quiescent morphology within a few weeks. Furthermore, imaging neurons simultaneously with microglia allows us to analyze the interactions of multiple cell types in the hippocampus. This technique may provide essential information about microglial function in the hippocampus.

In Vivo Chronic Two-Photon Imaging of Microglia in the Mouse Hippocampus

This paper describes a method for chronic in vivo observation of the resting microglia in the mouse hippocampal CA1 using precisely controlled surgery and two-photon microscopy.