Name: visual evoked potential recording in a rat model of experimental optic nerve demyelination
Uploaded: 2015-07-29T14:00:00.000+00:00
Duration: 6 min 49 s
Description: Watch this Scientific Journal Video about Visual Evoked Potential Recording in a Rat Model of Experimental Optic Nerve Demyelination at JoVE.com

This study was supported by the Ophthalmic Research Institute of Australia (ORIA). We thank Prof. Algis Vingrys and Dr. Bang Bui, University of Melbourne, for initially helping us to develop the VEP recording technique.

Ethics Statement: All procedures involving animals were conducted in accordance with the Australian Code of Practice for the Care and Use of Animals for Scientific Purposes and the guidelines of the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research, and were approved by the Animal Ethics Committee of Macquarie University.
1. VEP Electrode Implantation
<ol>
	<li>Anesthetize the animal with an intraperitoneal injection of ketamine (75 mg/kg) and medetomidine (0.5 mg/kg). 
	Note: Following induction of anaesthesia, observe the withdrawal reflexes (pinch test, corneal and palpebral reflex, etc.) and their absence as an indication to begin surgery. Continually monitor animals throughout the surgery and administer additional anaesthetic drug (10% of initial ketamine dose per top-up) if the reflexes are present. Adult rats (&#62;12 weeks) are used in the experiments.</li>
	<li>Shave the skin of the surgical area. Place the animal on a warming pad (37 &#176;C) to maintain body temperature during the surgery. Prepare skin through topical application of povidone-iodine. Apply surgical draping. Apply topical ophthalmic ointment to prevent corneal dryness under general anaesthesia. Maintain asepsis by using sterile instruments.</li>
	<li>Make a longitudinal skin incision on the midline of the head skin. Clear the connective tissue to achieve good exposure of the skull.</li>
	<li>Carefully, drill small burr holes manually using a micro hand drill at 7 mm behind the bregma and 3 mm lateral to the midline.</li>
	<li>Implant screw electrodes through the skull into the cortex (area 17), penetrating the cortex to a depth of approximately 0.5 mm. Implant a reference screw electrode on the midline 3 mm rostral to the bregma. Apply dental cement to encase and fix the screws (not always required).</li>
	<li>Suture the skin of the head, administer antibiotic ointment onto the skin and allow the animal to recover from anaesthesia on a warming pad. 
	Note: Alternatively, electrodes can be left exposed, so that skin doesn&#8217;t need to be reopened in each recording. Immediately upon cessation of surgery but prior to anaesthetic recovery, administer a non-steroidal anti-inflammatory drug (NSAID) (if not administered pre-operatively) or an opioid analgesic. Monitor the animals constantly until full recovery from anaesthetic and fully ambulatory.</li>
	<li>Allow at least 1 week for the animals to recover from the surgery prior to VEP recording.</li>
</ol>
2. Optic Nerve Injection
<ol>
	<li>Anesthetize the animal, prepare the skin and apply draping as above (1.1 and 1.2).</li>
	<li>Make a 1- to 1.5-cm incision in the skin above the orbit of a randomly selected eye. Open the subcutaneous tissue to reach the orbital cavity using fine iris scissors. Open the conjunctiva and anterior Tenon&#39;s capsule under the operating microscope.</li>
	<li>Retract the extraocular muscles and intraobital lacrimal glands to expose approximately 3 mm length of the optic nerve. Open the dura and arachnoid matter layers around the optic nerve longitudinally using an ophthalmic blade.</li>
	<li>Insert the glass pipette into the optic nerve at a distance of 2 mm posterior to the globe. The glass micropipette is attached to a Hamilton syringe.</li>
	<li>Inject 1% lysolecithin (0.4 - 1.0 &#181;l, with 0.02% Evan&#8217;s Blue which doesn&#8217;t have effects on myelination) slowly into the nerve approximately over a period of 30 sec.</li>
	<li>Suture the skin incision. Apply antibiotic ointment to prevent infection. Fellow eyes can be served as internal controls for electrophysiology recordings.</li>
	<li>Place the animals on a warming pad to recover from anaesthesia.</li>
</ol>
3. VEP Recording
<ol>
	<li>Anesthetize the animal and prepare the skin as 1.1 and 1.2. 
	Note: Lower dose of anaesthetics can be used for electrophysiological recording (ketamine 40 mg/kg and medetomidine 0.25 mg/kg).</li>
	<li>Place the rat in a dark room and allow it to adapt to darkness for 5 - 30 min. In some cases rats can respectively be dark adapted O/N for scotopic or light adapted for photopic VEP recordings8.</li>
	<li>Maintain the body temperature at 37 &#177; 0.5 &#176;C by the homoeothermic blanket system with a rectal thermometer probe.</li>
	<li>Dilate the pupils with 1.0% tropicamide eye drops. Open the skin over the skull to access the pre-placed in situ screw electrodes.</li>
	<li>Connect the screw over the contralateral visual cortex of the stimulated eye and the reference screw to the amplifier. Insert a needle electrode into the tail as the ground. Measure and maintain the electrode impedance below 5 k&#8486;.</li>
	<li>Place a mini-Ganzfeld stimulator directly on the skin around the eyelids to provide superior eye isolation7. The illumination of the stimulator needs to be calibrated beforehand by a photometer.</li>
	<li>Deliver photic stimulation through light flashes 100 times at a frequency of 1 Hz, with low and high band-pass filter settings of 1 and 100 Hz, respectively. The signal sampling rate is at 5 kHz. 
	Note: Signals should be sampled at least at about 250 - 300 Hz to ensure that more that two samples are collected during each cycle.</li>
	<li>Suture the skin back and keep the animals on a warming pad to recover from anaesthesia. Recording can be repeatedly recorded on individual animals to monitor functional changes over a period of time.</li>
	<li>At the end-point, administer an overdose injection of sodium pentobarbitone (100 mg/kg, i.p.) to euthanize the animal. Confirm euthanasia by cardiac arrest, respiratory arrest and decrease of body temperature.</li>
</ol>
4. Tissue Preparation and Histology
<ol>
	<li>Remove the optic nerves from euthanized animals under the microscope and fix the tissue in 1% paraformaldehyde O/N.</li>
	<li>Wash the tissue thoroughly with saline. Treat the tissue in an automatic tissue processor and embed in paraffin. Cut sections (5 - 10 &#181;m) using a rotary microtome. 
	Note: For immunohistochemistry study, fix tissue in 1% paraformaldehyde, wash with saline and incubate with 30% sucrose O/N. Embed tissue in OCT embedding medium and make cryosections using a cryostat.</li>
	<li>Incubate sections in 0.1% fast blue solution such as Luxol (in 95% ethanol) O/N at 56 &#176;C. Differentiate the sections in 0.05% lithium carbonate for 30 sec and then 70% ethanol for another 30 sec. Finally, counterstain in 0.1% cresyl violet solution for 30 sec before mounting the sections. Use the fast blue staining to identify myelin in the optic nerve5.</li>
</ol>

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I., Mushin, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Delayed+visual+evoked+response+in+optic+neuritis.">Delayed visual evoked response in optic neuritis.</a> Lancet. 1, 982-985 (1972).</li><li>You, Y., Klistorner, A., Thie, J., Graham, S. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Latency+delay+of+visual+evoked+potential+is+a+real+measurement+of+demyelination+in+a+rat+model+of+optic+neuritis.">Latency delay of visual evoked potential is a real measurement of demyelination in a rat model of optic neuritis.</a> Invest Ophthalmol Vis Sci. 52 (9), 6911-6918 (2011).</li><li>You, Y., Klistorner, A., Thie, J., Gupta, V. K., Graham, S. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Axonal+loss+in+a+rat+model+of+optic+neuritis+is+closely+correlated+with+visual+evoked+potential+amplitudes+using+electroencephalogram+based+scaling.">Axonal loss in a rat model of optic neuritis is closely correlated with visual evoked potential amplitudes using electroencephalogram based scaling.</a> Invest Ophthalmol Vis Sci. 53, 3662 (2012).</li><li>You, Y., Klistorner, A., Thie, J., Graham, S. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improving+reproducibility+of+VEP+recording+in+rats:+electrodes,+stimulus+source+and+peak+analysis.">Improving reproducibility of VEP recording in rats: electrodes, stimulus source and peak analysis.</a> Doc Ophthalmol. 123 (2), 109-119 (2011).</li><li>Heiduschka, P., Schraermeyer, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+visual+function+in+pigmented+and+albino+rats+by+electroretinography+and+visual+evoked+potentials.">Comparison of visual function in pigmented and albino rats by electroretinography and visual evoked potentials.</a> Graefes Arch Clin Exp Ophthalmol. 246 (11), 1559-1573 (2008).</li><li>You, Y., Thie, J., Klistorner, A., Gupta, V. K., Graham, S. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Normalization+of+visual+evoked+potentials+using+underlying+electroencephalogram+levels+improves+amplitude+reproducibility+in+rats.">Normalization of visual evoked potentials using underlying electroencephalogram levels improves amplitude reproducibility in rats.</a> Invest Ophthalmol Vis Sci. 53 (3), 1473-1478 (2012).</li><li>Levkovitch-Verbin, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Animal+models+of+optic+nerve+diseases.">Animal models of optic nerve diseases.</a> Eye (Lond). 18 (11), 1066-1074 (2004).</li><li>Henry, K. R., Rhoades, R. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Relation+of+albinism+and+drugs+to+the+visual+evoked+potential+of+the+mouse).">Relation of albinism and drugs to the visual evoked potential of the mouse).</a> J Comp Physiol Psychol. 92 (2), 271-279 (1978).</li><li>Murrell, J. C., Waters, D., Johnson, C. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparative+effects+of+halothane,+isoflurane,+sevoflurane+and+desflurane+on+the+electroencephalogram+of+the+rat.">Comparative effects of halothane, isoflurane, sevoflurane and desflurane on the electroencephalogram of the rat.</a> Lab Anim. 42 (2), 161-170 (2008).</li><li>Makela, K., Hartikainen, K., Rorarius, M., Jantti, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Suppression+of+F-VEP+during+isoflurane-induced+EEG+suppression.">Suppression of F-VEP during isoflurane-induced EEG suppression.</a> Electroencephalogr Clin Neurophysiol. 100 (3), 269-272 (1996).</li><li>Boyes, W. K., Padilla, S., Dyer, 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=Body+temperature-dependent+and+independent+actions+of+chlordimeform+on+visual+evoked+potentials+and+axonal+transport+in+optic+system+of+rat.">Body temperature-dependent and independent actions of chlordimeform on visual evoked potentials and axonal transport in optic system of rat.</a> Neuropharmacology. 24 (8), 743-749 (1985).</li><li>Hetzler, B. E., Boyes, W. K., Creason, J. P., Dyer, 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=Temperature-dependent+changes+in+visual+evoked+potentials+of+rats.">Temperature-dependent changes in visual evoked potentials of rats.</a> Electroencephalogr Clin Neurophysiol. 70 (2), 137-154 (1988).</li><li>Mitchell, J. <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+lysolecithin+on+non-myelinated+axons+in+vitro.">The effects of lysolecithin on non-myelinated axons in vitro.</a> Acta Neuropathol. 58 (4), 243-248 (1982).</li><li>Meyer, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Acute+neuronal+apoptosis+in+a+rat+model+of+multiple+sclerosis.">Acute neuronal apoptosis in a rat model of multiple sclerosis.</a> J Neurosci. 21 (16), 6214-6220 (2001).</li><li>Lachapelle, F., 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=Failure+of+remyelination+in+the+nonhuman+primate+optic+nerve.">Failure of remyelination in the nonhuman primate optic nerve.</a> Brain Pathol. 15 (3), 198-207 (2005).</li></ol>

None of the authors have competing interests or conflicting interests.

The optic nerve is very susceptible to mechanical damage. Optic nerve crush injury over a duration of 1 s can lead to about 75% loss of RGC over a period of 2 weeks10. Therefore, extreme care is required while performing the surgical procedures. According to the authors&#8217; experience, it is much better to adapt a blunt dissection approach to expose and make way through the tissues around the optic nerve along the orientation of the nerve, rather than penetrating in a perpendicular orientation to the optic nerve. Also, the dura and arachnoid mater should be unwraped longitudinally to avoid any axotomy-like damage to the RGC axons. Evan&#8217;s blue is usually used to facilitate the microinjection, as presence of the dye makes the nerve light blue in colour at the injection site.
The reproducibility of VEP recording is critical for this experiment. Different types of anaesthetics and the depth of anaesthesia can affect the VEP waveforms11. We do not recommend using inhaled isoflurane anaesthesia for the VEP study, as isoflurane can lead to burst suppress on the electroencephalogram response12, probably due to GABAergic activity, resulting in more variable VEP traces13. Combination of ketamine/medetomidine anaesthesia provides stable anaesthesia that can quickly be reversed by administration of an alpha receptor antagonist such as atipamazole (2.5 mg/kg i.p). Body temperature can also have a significant impact on the speed of nerve conduction, especially in demyelinated nerves. Temperature-dependant changes in visual evoked potentials have been observed in rat VEPs and latencies were observed to be significantly longer as body temperature was lowered14,15. Hence, it is important to maintain a uniform body temperature using a homoeothermic blanket system during the VEP recordings.
Also, it is important to understand that the pathogenesis of lysolecithin-induced demyelination differs from that in optic neuritis or multiple sclerosis. Lysolecithin-induced demyelination results from the detergent like action of the toxin upon myelin lipids rather than immune-mediated inflammatory reaction, which is usually seen in the real disease scenarios16. If the study aims to investigate the mechanisms of demyelination/axonal damage in multiple sclerosis, an immune-mediated demyelination model, such as experimental autoimmune encephalomyelitis (EAE)17, should be considered. The advantage of using the toxin-induced demyelination model is that a focal lesion in the optic nerve can be produced and monitored longitudinally. In contrast to the brain lesions, the effects of demyelinated lesions on the optic nerve are more clinically apparent and measureable (lesion size can be accurately determined by VEPs or MRI imaging). Although remyelination in the optic nerve appeared to be not as pronounced as that observed previously in the case of spinal cord18, this optic nerve injection model, in conjunction with the VEP recording technique, is able to provide a superior tool to monitor the process of demyelination and remyelination in vivo, and to potentially evaluate new remyelinating therapies.

Optic neuritis is one of the most common form of optic neuropathy, causing complete or partial loss of vision1. Histologically, it is featured by inflammatory demyelination, retinal ganglion cell axonal loss and varying degrees of remyelination in the optic nerve2. Optic neuritis is usually the manifest onset of multiple sclerosis. The visual evoked potential (VEP) is a non-invasive tool for investigating the function of the visual system. It reflects the post-retinal function from the retina to the primary visual cortex and is affected in many optic nerve disease conditions3. The VEP has been predominantly used in optic neuritis patients to assess the integrity of the visual pathway4. 
The latency of VEP, which reflects the velocity of signal conduction along the visual pathway, is considered to be an accurate measurement of the level of myelin associated changes in the optic nerve5; while the amplitude of VEP is believed to be closely correlated with axonal damage of the retinal ganglion cells (RGC)6. This hypothesis has been fairly well established using the rat model of lysolecithin-induced optic nerve demyelination5. 
Here, we explicate a comprehensive protocol of optic nerve microinjection technique in rodents, which can minimise the surgical manipulation-related damage to the nerve per se as well as to the adjacent tissues such as extraocular muscles and blood vessels. Also, the skull electrode implantation surgery has been described for VEP recording in animals7. The VEP recordings can be repeatedly carried out on animals over a period of time to assess demyelination/remyelination related changes as well as impact on axonal integrity in the optic nerve.

<table><tbody><tr><td>Ketamine 100 mg/ml (Ketamil)</td><td>Troy Laboratories</td><td>AC 116</td><td></td></tr><tr><td>Medetomidine 1 mg/ml (Domitor)</td><td>Pfizer</td><td>sc-204073</td><td></td></tr><tr><td>Tropicamide 1.0% (Mydriacyl)</td><td>Alcon</td><td>sc-202371</td><td></td></tr><tr><td>Homoeothermic blanket system</td><td>Harvard Apparatus</td><td>NC9203819</td><td></td></tr><tr><td>Impedance meter&amp;nbsp;</td><td>Grass</td><td>F-EZM5</td><td></td></tr><tr><td>Screw electrodes&amp;nbsp;</td><td>Micro Fasteners</td><td>M1.0&amp;times;3mm Csk Slot M/T 304 S/S</td><td></td></tr><tr><td>Subdermal needle electrodes&amp;nbsp;</td><td>Grass</td><td>F-E3M-72</td><td></td></tr><tr><td>Rapid Repair&amp;nbsp;</td><td>DeguDent GmbH</td><td></td><td></td></tr><tr><td>Light-emitting diode&amp;nbsp;</td><td>Nichia</td><td>NSPG300A</td><td></td></tr><tr><td>Bioamplifier</td><td>CWE, Inc.</td><td>BMA-400</td><td></td></tr><tr><td>CED system</td><td>Cambridge Electronic Design, Ltd.</td><td>Power1401</td><td></td></tr><tr><td>Hamilton syringe&amp;nbsp;</td><td>Hamilton</td><td>87930</td><td></td></tr><tr><td>Lysolecithin</td><td>Sigma</td><td>L4129</td><td></td></tr><tr><td>Evan&amp;rsquo;s blue&amp;nbsp;</td><td>Sigma</td><td>E2129</td><td></td></tr></tbody></table>

visual evoked potential recording in a rat model of experimental optic nerve demyelination

The visual evoked potential (VEP) recording is widely used in clinical practice to assess the severity of optic neuritis in its acute phase, and to monitor the disease course in the follow-up period. Changes in the VEP parameters closely correlate with pathological damage in the optic nerve. This protocol provides a detailed description about the rodent model of optic nerve microinjection, in which a partial demyelination lesion is produced in the optic nerve. VEP recording techniques are also discussed. Using skull implanted electrodes, we are able to acquire reproducible intra-session and between-session VEP traces. VEPs can be recorded on individual animals over a period of time to assess the functional changes in the optic nerve longitudinally. The optic nerve demyelination model, in conjunction with the VEP recording protocol, provides a tool to investigate the disease processes associated with demyelination and remyelination, and can potentially be employed to evaluate the effects of new remyelinating drugs or neuroprotective therapies.

Reproducible intra-sessional VEP traces are shown in Figure 1 and a significant delay in N1 latency can be seen after the optic nerve injection. Partial optic nerve lesions of demyelination can be observed on histological sections using Luxol fast blue staining5. Figure 2 shows a representative section with a small focal demyelinated lesion in the centre of the optic nerve. Note that cross section does not represent total volume of lesion. The demyelinated area can be measured on each consecutive cross-section of the nerve to deduce the lesion volume by using three-dimensional reconstruction. We have demonstrated a strong correlation between latency delay and lesion volume using this model in our previous studies and there was no VEP latency delay in the saline-injected controls5.
It is believed that early VEP components following the flash illumination are more stable7 and principally affected by the excitation of the primary visual cortex via retino-geniculate fibres. Our study has shown that N1 delay has the strongest linear relationship with demyelination in the optic nerve5. Hence, we recommend that N1 latency should be used for data analysis and for longitudinal VEP monitoring in assessing the impact of remyelinating therapies. The amplitude of VEP, although more variable compared to the latency, is more indicative of function of the axons in the optic nerve6. Electroencephalogram-based scaling can be considered for amplitude analysis9.
<img alt="Figure 1" src="/files/ftp_upload/52934/52934fig1.jpg" /> 
Figure 1.&#160;VEP delay after optic nerve injection. Representative VEP traces from an individual rat before and 2 days after the optic nerve microinjection (0.8 &#181;l lysolecithin). VEP recordings were repeated on the each day (intra-sessional traces are shown in the same colour) to demonstrate the reproducibility of this VEP recording protocol. (vertical scale bar: 10 &#181;V; horizontal scale bar: 10 msec). <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/52934/52934fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure2" src="/files/ftp_upload/52934/52934fig2.jpg" /> 
Figure 2.&#160;Demyelination in the optic nerve. Representative cross-section of the optic nerve from a rat after lysolecithin microinjection. The myelin component is stained blue by using luxol fast blue. A small focal lesion of demyelination can be seen in the centre of the section. Demyelinated area can be measured on longitudinal serial cross-sections to estimate the lesion volume in a three-dimensional scale. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/52934/52934fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Visual Evoked Potential Recording in a Rat Model of Experimental Optic Nerve Demyelination at JoVE.com

Visual Evoked Potential Recording in a Rat Model of Experimental Optic Nerve Demyelination

Focal demyelination is induced in the optic nerve using lysolecithin microinjection. Visual evoked potentials are recorded via skull electrodes implanted over the visual cortex to examine the signal conduction along the visual pathway in vivo. This protocol details the surgical procedures underlying electrode implantation and optic nerve microinjection.

The visual evoked potential (VEP) recording is widely used in clinical practice to assess the severity of optic neuritis in its acute phase, and to ...

visual-evoked-potential-recording-rat-model-experimental-optic-nerve

Universidad San Sebastian

Research

JoVE Journal

Neuroscience

12.2K Views.  Macquarie University. Focal demyelination is induced in the optic nerve using lysolecithin microinjection. Visual evoked potentials are recorded via skull electrodes implanted over the visual cortex to examine the signal conduction along the visual pathway in vivo. This protocol details the surgical procedures underlying electrode implantation and optic nerve microinjection. 

Video: Visual Evoked Potential Recording in a Rat Model of Experimental Optic Nerve Demyelination

Single-unit In vivo Recordings from the Optic Chiasm of Rat

Information about the visual world is transmitted to the brain in sequences of action potentials in retinal ganglion cell axons that make up the optic nerve. In vivo recordings of ganglion cell spike trains in several animal models have revealed much of what is known about how the early visual system processes and encodes visual information. However, such recordings have been rare in one of the most common animal models, the rat, possibly owing to difficulty in detecting spikes fired by small diameter axons. The many retinal disease models involving rats motivate a need for characterizing the functional properties of ganglion cells without disturbing the eye, as with intraocular or in vitro recordings. Here, we demonstrate a method for recording ganglion cell spike trains from the optic chiasm of the anesthetized rat. We first show how to fabricate tungsten-in-glass electrodes that can pick up electrical activity from single ganglion cell axons in rat. The electrodes outperform all commercial ones that we have tried. We then illustrate our custom-designed stereotaxic system for in vivo visual neurophysiology experiments and our procedures for animal preparation and reliable and stable electrode placement in the optic chiasm.

Single-unit In vivo Recordings from the Optic Chiasm of Rat

Retinal ganglion cells transmit visual information from the eye to the brain with sequences of action potentials. Here, we demonstrate how to record the action potentials of single ganglion cells in vivo from anesthetized rats.

Information about the visual world is transmitted to the brain in sequences of action potentials in retinal ganglion cell axons that make up the optic ...

Implantation and Recording of Wireless Electroretinogram and Visual Evoked Potential in Conscious Rats

The full-field electroretinogram (ERG) and visual evoked potential (VEP) are useful tools to assess retinal and visual pathway integrity in both laboratory and clinical settings. Currently, preclinical ERG and VEP measurements are performed with anesthesia to ensure stable electrode placements. However, the very presence of anesthesia has been shown to contaminate normal physiological responses. To overcome these anesthesia confounds, we develop a novel platform to assay ERG and VEP in conscious rats. Electrodes are surgically implanted sub-conjunctivally on the eye to assay the ERG and epidurally over the visual cortex to measure the VEP. A range of amplitude and sensitivity/timing parameters are assayed for both the ERG and VEP at increasing luminous energies. The ERG and VEP signals are shown to be stable and repeatable for at least 4 weeks post surgical implantation. This ability to record ERG and VEP signals without anesthesia confounds in the preclinical setting should provide superior translation to clinical data.

We show surgical implantation and Recording procedures to measure visual electrophysiological signals from the eye (electroretinogram) and brain (visual evoked potential) in conscious rats, which is more analogous to the human condition where recordings are conducted without anesthesia confounds.

The full-field electroretinogram (ERG) and visual evoked potential (VEP) are useful tools to assess retinal and visual pathway integrity in both ...

Behavior

Rat Model of Photochemically-Induced Posterior Ischemic Optic Neuropathy

Posterior Ischemic optic neuropathy (PION) is a sight-devastating disease in clinical practice. However, its pathogenesis and natural history have&#160;remained poorly understood. Recently, we developed a reliable, reproducible animal model of PION and tested the treatment effect of some neurotrophic factors in this model1. The purpose of this video is to demonstrate our photochemically induced model of posterior ischemic optic neuropathy, and to evaluate its effects with retrograde labeling of retinal ganglion cells. Following surgical exposure of the posterior optic nerve, a photosensitizing dye, erythrosin B, is intravenously injected and a laser beam is focused onto the optic nerve surface. Photochemical interaction of erythrosin B and the laser during irradiation damages the vascular endothelium, prompting microvascular occlusion mediated by platelet thrombosis and edematous compression. The resulting ischemic injury yields a gradual but pronounced retinal ganglion cell dieback, owing to a loss of axonal input - a remote, injury-induced and clinically relevant outcome. Thus, this model provides a novel platform to study the pathophysiologic course of PION,&#160;and can be further optimized for testing therapeutic approaches for optic neuropathies as well as other CNS ischemic diseases.

The goal of this protocol is to photochemically induce ischemic injury to the posterior optic nerve in rat. This model is critical to studies of the pathophysiology of posterior ischemic optic neuropathy, and therapeutic approaches for this and other optic neuropathies, as well as of other CNS ischemic diseases.

Posterior Ischemic optic neuropathy (PION) is a sight-devastating disease in clinical practice. However, its pathogenesis and natural history ...

Medicine

Simultaneous Recording of Electroretinography and Visual Evoked Potentials in Anesthetized Rats

The electroretinogram (ERG) and visual evoked potential (VEP) are commonly used to assess the integrity of the visual pathway. The ERG measures the electrical responses of the retina to light stimulation, while the VEP measures the corresponding functional integrity of the visual pathways from the retina to the primary visual cortex following the same light event. The ERG waveform can be broken down into components that reflect responses from different retinal neuronal and glial cell classes. The early components of the VEP waveform represent the integrity of the optic nerve and higher cortical centers. These recordings can be conducted in isolation or together, depending on the application. The methodology described in this paper allows simultaneous assessment of retinal and cortical visual evoked electrophysiology from both eyes and both hemispheres. This is a useful way to more comprehensively assess retinal function and the upstream effects that changes in retinal function can have on visual evoked cortical function.

This protocol describes simultaneous measurement of electroretinogram and visual evoked potentials in anesthetized rats.

The electroretinogram (ERG) and visual evoked potential (VEP) are commonly used to assess the integrity of the visual pathway. The ERG measures the ...

Visual Evoked Potential Recordings in Mice Using a Dry Non-invasive Multi-channel Scalp EEG Sensor

For scalp EEG research environments with laboratory mice, we designed a dry-type 16 channel EEG sensor which is non-invasive, deformable, and re-usable because of the plunger-spring-barrel structural facet and mechanical strengths resulting from metal materials. The whole process for acquiring the VEP responses in vivo from a mouse consists of four steps: (1) sensor assembly, (2) animal preparation, (3) VEP measurement, and (4) signal processing. This paper presents representative measurements of VEP responses from multiple mice with a submicro-voltage signal resolution and sub-hundred millisecond temporal resolution. Although the proposed method is safer and more convenient compared to other previously reported animal EEG acquiring methods, there are remaining issues including how to enhance the signal-to-noise ratio and how to apply this technique with freely moving animals. The proposed method utilizes easily available resources and shows a repetitive VEP response with a satisfactory signal quality. Therefore, this method could be utilized for longitudinal experimental studies and reliable translational research exploiting non-invasive paradigms.

We designed a dry-type 16 channel EEG sensor which is non-invasive, deformable, and re-usable. This paper describes the whole process from manufacturing the proposed EEG electrode to signal processing of visual evoked potential (VEP) signals measured on a mouse scalp using a dry non-invasive multi-channel EEG sensor.

For scalp EEG research environments with laboratory mice, we designed a dry-type 16 channel EEG sensor which is non-invasive, deformable, and re-usable ...

In Vivo Methods to Assess Retinal Ganglion Cell and Optic Nerve Function and Structure in Large Animals

The optic nerve collects axons signals from the retinal ganglion cells and transmits visual signal to the brain. Large animal models of optic nerve injury are essential for translating novel therapeutic strategies from rodent models to clinical application due to their closer similarities to humans in size and anatomy. Here we describe some in vivo methods to evaluate the function and structure of the retinal ganglion cells (RGCs) and optic nerve (ON) in large animals, including visual evoked potential (VEP), pattern electroretinogram (PERG) and optical coherence tomography (OCT). Both goat and non-human primate were employed in this study. By presenting these in vivo methods step by step, we hope to increase experimental reproducibility among different labs and facilitate the usage of large animal models of optic neuropathies.

In Vivo Methods to Assess Retinal Ganglion Cell and Optic Nerve Function and Structure in Large Animals

Here we demostrate several in vivo tests (flash visual evoked potential, pattern electroretinogram and optic coherence tomography) in goat and rhesus macaque to understand the structure and function of the optic nerve and its neurons.

The optic nerve collects axons signals from the retinal ganglion cells and transmits visual signal to the brain. Large animal models of optic nerve injury ...

Inducing Local Demyelination in the Optic Nerve Using Lysolecithin

Source: You, Y. et al., <a href="https://app-jove-com.bdigitaluss.remotexs.co/v/52934">Visual Evoked Potential Recording in a Rat Model of Experimental Optic Nerve Demyelination.</a> J. Vis. Exp. (2015)
This video demonstrates the procedure of surgically accessing the optic nerve in an anesthetized animal and precisely delivering lysolecithin to induce focal demyelination, creating neuropathological conditions for further study.

All procedures involving animal models have been reviewed by the local institutional animal care committee and the JoVE veterinary review board. ...

JoVE Encyclopedia of Experiments

Neuropathology

Epilepsy and Seizure Disorders

Preparing a Rat Model to Assess Visual Pathway Integrity Using an Electrophysiology Setup

Source: Nguyen, C. T. et al., <a href="https://app-jove-com.bdigitaluss.remotexs.co/v/54158">Simultaneous Recording of Electroretinography and Visual Evoked Potentials in Anesthetized Rats.</a>&#160;J. Vis. Exp. (2016)
This video demonstrates the preparation of a rat model to study retinal health and visual pathway integrity. Visual evoked potential and electroretinography reference and active electrodes are connected to the rat, followed by aligning the platform with the rat in front of the Ganzfeld bowl for even retinal illumination and closing the Faraday cage to avoid external interference.

All procedures involving animal models have been reviewed by the local institutional animal care committee and the JoVE veterinary review board.
1. ...

Neurophysiology

Electrophysiology Techniques

Electron Microscopic Analysis of Myelin Damage in a Rat Model of Optic Nerve Injury

Take fixed optic nerve sections from a control rat and a rat with optic nerve injury.
The control section exhibits axons with tightly packed myelin sheaths containing concentric plasma membrane layers. The injured section exhibits decompacted myelin with large gaps.
Incubate with an osmium-ferrocyanide complex that binds to lipids and enhances the myelin sheath&#39;s contrast.
Treat with thiocarbohydrazide to create additional binding sites for osmium.
Reapply osmium to further enhance lipid contrast.
Stain with heavy metals, which bind to macromolecules and enhance structural contrast.
Dehydrate using increasing alcohol concentrations and rinse with acetone for resin embedding.
Embed the tissue in resin, and coat the resin with gold to improve image quality.
Use serial block-face scanning electron microscopy to simultaneously slice and image. Focus the electron beam on the surface and detect the backscattered electrons to generate images.
Myelin sheaths appear dark, while spaces within damaged sheaths appear lighter, allowing differentiation between normal and damaged myelin.

Neuromuscular Disorders

Recording of Visual Evoked Potentials via the Skull Electrodes in a Rat Model

Source: You, Y., et al. <a href="https://app-jove-com.bdigitaluss.remotexs.co/v/52934">Visual Evoked Potential Recording in a Rat Model of Experimental Optic Nerve Demyelination.</a> J. Vis. Exp. (2015).
This video demonstrates the process of measuring visual evoked potentials or VEPs in a dark-adapted, anesthetized rat with pre-implanted skull electrodes, which record the electrical signals from the brain&#39;s visual cortex in response to light stimuli.

All procedures involving animal models have been reviewed by the local institutional animal care committee and the JoVE veterinary review board.
1. VEP ...

Visual Evoked Potential Recording in a Rat Model of Experimental Optic Nerve Demyelination

Summary

Explore More Videos

Chapters in this video

Single-unit In vivo Recordings from the Optic Chiasm of Rat

Implantation and Recording of Wireless Electroretinogram and Visual Evoked Potential in Conscious Rats

Rat Model of Photochemically-Induced Posterior Ischemic Optic Neuropathy

Simultaneous Recording of Electroretinography and Visual Evoked Potentials in Anesthetized Rats

Visual Evoked Potential Recordings in Mice Using a Dry Non-invasive Multi-channel Scalp EEG Sensor

In Vivo Methods to Assess Retinal Ganglion Cell and Optic Nerve Function and Structure in Large Animals

Inducing Local Demyelination in the Optic Nerve Using Lysolecithin

Preparing a Rat Model to Assess Visual Pathway Integrity Using an Electrophysiology Setup

Electron Microscopic Analysis of Myelin Damage in a Rat Model of Optic Nerve Injury

Recording of Visual Evoked Potentials via the Skull Electrodes in a Rat Model