Work supported by NIH grant AG027297, an award from the Kentucky Spinal Cord and Head Injury Research Trust, and a gift from the Kleberg Foundation.

<ol>
	<li>Norris, C. M., Halpain, S., Foster, T. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alterations+in+the+balance+of+protein+kinase/phosphatase+activities+parallel+reduced+synaptic+strength+during+aging.">Alterations in the balance of protein kinase/phosphatase activities parallel reduced synaptic strength during aging.</a> J Neurophysiol. 80, 1567-1570 (1998).</li><li>Norris, C. M., Korol, D. L., Foster, T. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Increased+susceptibility+to+induction+of+long-term+depression+and+long-term+potentiation+reversal+during+aging.">Increased susceptibility to induction of long-term depression and long-term potentiation reversal during aging.</a> J Neurosci. 16, 5382-5392 (1996).</li><li>Norris, C. 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A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interleukin-1beta-dependent+signaling+between+astrocytes+and+neurons+depends+critically+on+astrocytic+calcineurin/NFAT+activity.">Interleukin-1beta-dependent signaling between astrocytes and neurons depends critically on astrocytic calcineurin/NFAT activity.</a> J Biol Chem. 283, 21953-21964 (2008).</li><li>Ye, H., Jalini, S., Mylvaganam, S., Carlen, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Activation+of+large-conductance+Ca(2+)-activated+K(+)+channels+depresses+basal+synaptic+transmission+in+the+hippocampal+CA1+area+in+APP+(swe/ind)+TgCRND8+mice.">Activation of large-conductance Ca(2+)-activated K(+) channels depresses basal synaptic transmission in the hippocampal CA1 area in APP (swe/ind) TgCRND8 mice.</a> Neurobiol Aging. 31, 591-604 (2010).</li><li>Bear, M. F., Malenka, R. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synaptic+plasticity:+LTP+and+LTD.">Synaptic plasticity: LTP and LTD.</a> Curr Opin Neurobiol. 4, 389-399 (1994).</li><li>Foster, T. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Involvement+of+hippocampal+synaptic+plasticity+in+age-related+memory+decline.">Involvement of hippocampal synaptic plasticity in age-related memory decline.</a> Brain Res Brain Res Rev. 30, 236-249 (1999).</li><li>Foster, T. C., Kumar, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Susceptibility+to+induction+of+long-term+depression+is+associated+with+impaired+memory+in+aged+Fischer+344+rats.">Susceptibility to induction of long-term depression is associated with impaired memory in aged Fischer 344 rats.</a> Neurobiol Learn Mem. 87, 522-535 (2007).</li><li>Hsu, K. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alterations+in+the+balance+of+protein+kinase+and+phosphatase+activities+and+age-related+impairments+of+synaptic+transmission+and+long-term+potentiation.">Alterations in the balance of protein kinase and phosphatase activities and age-related impairments of synaptic transmission and long-term potentiation.</a> Hippocampus. 12, 787-802 (2002).</li><li>Vouimba, R. M., Foy, M. R., Foy, J. G., Thompson, R. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=17beta-estradiol+suppresses+expression+of+long-term+depression+in+aged+rats.">17beta-estradiol suppresses expression of long-term depression in aged rats.</a> Brain Res Bull. 53, 783-787 (2000).</li><li>Abdul, H. M., Furman, J. L., Sama, M. A., Mathis, D. M., Norris, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=NFATs+and+Alzheimer's+Disease.">NFATs and Alzheimer's Disease.</a> Mol Cell Pharmacol. 2, 7-14 (2010).</li><li>Abdul, H. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cognitive+decline+in+Alzheimer's+disease+is+associated+with+selective+changes+in+calcineurin/NFAT+signaling.">Cognitive decline in Alzheimer's disease is associated with selective changes in calcineurin/NFAT signaling.</a> J Neurosci. 29, 12957-12969 (2009).</li><li>Anantharaman, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Beta-amyloid+mediated+nitration+of+manganese+superoxide+dismutase:+implication+for+oxidative+stress+in+a+APPNLH/NLH+X+PS-1P264L/P264L+double+knock-in+mouse+model+of+Alzheimer's+disease.">Beta-amyloid mediated nitration of manganese superoxide dismutase: implication for oxidative stress in a APPNLH/NLH X PS-1P264L/P264L double knock-in mouse model of Alzheimer's disease.</a> Am J Pathol. 168, 1608-1618 (2006).</li><li>Gengler, S., Hamilton, A., Holscher, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synaptic+plasticity+in+the+hippocampus+of+a+APP/PS1+mouse+model+of+Alzheimer's+disease+is+impaired+in+old+but+not+young+mice.">Synaptic plasticity in the hippocampus of a APP/PS1 mouse model of Alzheimer's disease is impaired in old but not young mice.</a> PLoS One. 5, e9764-e9764 (2010).</li><li>Stringer, J. L., Lothman, E. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vitro+effects+of+extracellular+calcium+concentrations+on+hippocampal+pyramidal+cell+responses.">In vitro effects of extracellular calcium concentrations on hippocampal pyramidal cell responses.</a> Exp Neurol. 101, 132-146 (1988).</li><li>Landfield, P. W., Pitler, T. A., Applegate, M. D. <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+high+Mg2+-to-Ca2++ratios+on+frequency+potentiation+in+hippocampal+slices+of+young+and+aged+rats.">The effects of high Mg2+-to-Ca2+ ratios on frequency potentiation in hippocampal slices of young and aged rats.</a> J Neurophysiol. 56, 797-811 (1986).</li><li>Ames, A., Sakanoue, M., Endo, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=NA,+K,+CA,+MG,+AND+C1+CONCENTRATIONS+IN+CHOROID+PLEXUS+FLUID+AND+CISTERNAL+FLUID+COMPARED+WITH+PLASMA+ULTRAFILTRATE.">NA, K, CA, MG, AND C1 CONCENTRATIONS IN CHOROID PLEXUS FLUID AND CISTERNAL FLUID COMPARED WITH PLASMA ULTRAFILTRATE.</a> J Neurophysiol. 27, 672-681 (1964).</li><li>Gant, J. C., Sama, M. M., Landfield, P. 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E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhanced+ryanodine+receptor+recruitment+contributes+to+Ca2++disruptions+in+young,+adult,+and+aged+Alzheimer's+disease+mice.">Enhanced ryanodine receptor recruitment contributes to Ca2+ disruptions in young, adult, and aged Alzheimer's disease mice.</a> J Neurosci. 26, 5180-5189 (2006).</li><li>Lee, H. K., Min, S. S., Gallagher, M., Kirkwood, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=NMDA+receptor-independent+long-term+depression+correlates+with+successful+aging+in+rats.">NMDA receptor-independent long-term depression correlates with successful aging in rats.</a> Nat Neurosci. 8, 1657-1659 (2005).</li><li>McNaughton, B. L., Douglas, R. M., Goddard, G. 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The production of this video-article was sponsored by Leica Microsystems.

The steps outlined in this protocol will help insure that brain dissections are carried out at least as rapidly and efficiently in aged, as in young adult rats. We also provide sufficient detail for the beginner to set up their own slice studies on LTP and LTD. If further exploration of aging and AD changes in synaptic function and plasticity is one of your goals, there are at least two other methodological issues, alluded to above, that deserve further consideration. First, several labs have shown that the Ca2+:Mg2+ ratio in recording ACSF can have a marked effect on the induction synaptic plasticity in hippocampal slices2,10,24,25. In mammalian CSF, the Ca2+:Mg2+ ratio is approximately one (e.g. see 26). However, ACSF Ca2+:Mg2+ ratios closer to 2 are commonly used in slice studies of synaptic function and plasticity. In early studies, this practice was probably adapted to optimize induction of LTP, then subsequently became routine for all plasticity studies. However, this practice can be problematic in aging and AD studies because of well-characterized differences in neuronal Ca2+ regulation. Specifically, Ca2+ influx and/or Ca2+-induced Ca2+-release is elevated in aged rats and/or AD model mice during neuronal activation3,27-31. Induction of LTD is particularly sensitive to subtle changes in ACSF Ca2+ levels. Our protocol, which uses 2mM Ca2+ and 2 mM Mg2+, commonly results in LTD for aged, but not young adult animals2, while studies using a Ca2+:Mg2+ ratio closer to two, have observed robust LTD in adults in the absence of an age difference2,10 or in conjunction with reduced LTD in aged rats32. These observations highlight the need to carefully consider ACSF Ca2+ and Mg2+ levels when comparing Ca2+-dependent plasticity in aged and young adult animals.
The second methodological issue concerns the strong dependency of LTP on postsynaptic depolarization33 and possible aging/genotype differences in synaptic strength. In a typical LTP experiment, baseline and LTP stimulation intensity is generally adjusted to produce a half maximal (or three-quarter maximal) EPSP amplitude. The potential problem is that aged rats and APP/PS1 mice usually show reduced synaptic strength relative to their younger and/or wild type counterparts, meaning that baseline EPSP values will also be smaller in aged rats and APP/PS1 mice. Smaller EPSPs may translate to less depolarization during LTP stimulation, resulting in a reduced probability for inducing LTP33. Because of this potential confound, it is difficult to determine whether these animals exhibit a throughput deficit, a plasticity deficit or both. That is, LTP induction mechanisms in aged and/or APP/PS1 mice may be functionally intact (no plasticity deficit), but insufficiently stimulated (throughput deficit) under these conditions. This distinction is critical, as mechanisms for throughput and mechanisms for plasticity may respond very differently to a specific pharmacologic treatment. We try to minimize the impact of reduced throughput on LTP induction by normalizing the EPSP amplitude to the same level (e.g. 1 mV) across all slices prior to LTP stimulation. Other strategies may be effective as well (e.g. use of voltage or current clamp to equalize the membrane potential across groups during LTP stimulation), and should be considered when investigating LTP in these animal models.

<table border="1">
<tbody>
 <tr>
 <td>Name of the reagent</td>
 <td>Company</td>
 <td>Catalogue number</td>
 </tr>
 <tr>
 <td>NaCl</td>
 <td>Fisher</td>
 <td>BP358-1</td>
 </tr>
 <tr>
 <td>KCl</td>
 <td>Fisher</td>
 <td>BP366-500</td>
 </tr>
 <tr>
 <td>KH2PO4 (monobasic)</td>
 <td>Sigma</td>
 <td>P5379-100G</td>
 </tr>
 <tr>
 <td>MgSO4</td>
 <td>Sigma</td>
 <td>M2643-500G</td>
 </tr>
 <tr>
 <td>CaCl2 (dihydrate)</td>
 <td>Sigma </td>
 <td>C3306-250G</td>
 </tr>
 <tr>
 <td>NaHCO3</td>
 <td>Fisher </td>
 <td>S233-500</td>
 </tr>
 <tr>
 <td>C6H12O6 (dextrose)</td>
 <td>Fisher </td>
 <td>BP350-1</td>
 </tr>
</tbody>
</table>
Table 1. Reagents required
<table border="1">
<tbody>
 <tr>
 <td>Name of the equipment</td>
 <td>Company</td>
 <td>Catalogue number</td>
 <td>Comments </td>
 </tr>
 <tr>
 <td>Erlenmeyer Flasks</td>
 <td>Fisher</td>
 <td>FB-500-2000 
 FB-500-1000</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Aquarium Bubbler</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 <td>Used for oxygenating media. Available at most pet stores</td>
 </tr>
 <tr>
 <td>50 mL Glass beaker</td>
 <td>Fisher</td>
 <td>02-540G</td>
 <td>For brain storarge in ACSF</td>
 </tr>
 <tr>
 <td>Parafilm</td>
 <td>Fisher</td>
 <td>13-374-10</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Small Animal Guillotine</td>
 <td>World Precision Instruments (WPI)</td>
 <td>DCAP-M</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Flat paper towel</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>#11 Feather surgical blade</td>
 <td>Fisher</td>
 <td>08-916-5B</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Beebee bone scissors</td>
 <td>Fine Science Tools (FST)</td>
 <td>16044-10</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Lempert Rongeurs</td>
 <td>Roboz</td>
 <td>RS-8321</td>
 <td>Use for rats</td>
 </tr>
 <tr>
 <td>Friedman-Pearson Rongeurs</td>
 <td>FST</td>
 <td>16020-14</td>
 <td>Use for mice or rats</td>
 </tr>
 <tr>
 <td>Hippocampus tool</td>
 <td>FST</td>
 <td>10099-15</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Spoon</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 <td>A plastic teaspoon will do</td>
 </tr>
 <tr>
 <td>Spatula</td>
 <td>Fisher</td>
 <td>21-401-25A </td>
 <td>Spatula</td>
 </tr>
 <tr>
 <td>Surgical iris scissors</td>
 <td>FST</td>
 <td>14058-09</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>plastic transfer pipets</td>
 <td>Fisher</td>
 <td>13-711-43 </td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>110mm Whatman filter paper</td>
 <td>Fisher</td>
 <td>09-805E</td>
 <td>Whatman cat. 1001-110</td>
 </tr>
 <tr>
 <td>Glass petri dish</td>
 <td>Fisher</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td><a href="http://www.leica-microsystems.com/products/total-histology/sectioning/vibrating-blade-microtomes/">Leica VT1000P Manual Vibrating Microtome</a></td>
 <td>Vibratome</td>
 <td>VT1000P</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>0.1mm FA-10 Feather S blade</td>
 <td>Ted Pella</td>
 <td>121-9</td>
 <td>0.1mm FA-10 Feather S blade</td>
 </tr>
 <tr>
 <td>Borosilicate Glass Pasteur Pipet (with rubber bulb)</td>
 <td>Fisher</td>
 <td>13-678-20A</td>
 <td>For transferring slices: Tip is broken off and heat-polished for larger opening</td>
 </tr>
 <tr>
 <td>35 mm Polysterine Culture dish</td>
 <td>Corning</td>
 <td>430588</td>
 <td>Used for collecting slices after dissection</td>
 </tr>
</tbody>
</table>
Table 2. Tools and materials for dissection
<table border="1">
<tbody>
 <tr>
 <td>Equipment/Materials</td>
 <td>Company</td>
 <td>Comments (optional)</td>
 </tr>
 <tr>
 <td>Holding chamber</td>
 <td>Custom Built</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>P-97 Horizontal Pipette Puller</td>
 <td>Sutter Instrument Co.</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Vibration isolation table</td>
 <td>Technical Manufacturing Corporation (TMC)</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Faraday cage</td>
 <td>Custom built</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Pyrex Aspirator Bottle with Bottom Sidearm (Product #1220-1L)</td>
 <td>Corning</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Gravity-contolled IV set with regulator (Product # 2C8891)</td>
 <td>Baxter</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Central Vacuum Line</td>
 <td>&nbsp;</td>
 <td>Available in most modern labs</td>
 </tr>
 <tr>
 <td>95% O2 / 5% CO2 Gas Mix </td>
 <td>Scott-Gross Co.</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>TygonTM Lab tubing 
 For O2/CO2 delivery</td>
 <td>Fisher Scientific</td>
 <td>Non-toxic, non-oxidizing, comes in a variety of sizes.</td>
 </tr>
 <tr>
 <td>Eclipse E600FN Microscope</td>
 <td>Nikon</td>
 <td>with 10x and 40x objectives, near infared filter, and GFP,DS-Red2 filters</td>
 </tr>
 <tr>
 <td>Cool Snap ES Digital Camera</td>
 <td>Photometrics</td>
 <td>Cool Snap ES Digital Camera</td>
 </tr>
 <tr>
 <td>X-Cite Fluorescent Illuminator</td>
 <td>EXFO</td>
 <td>X-Cite Fluorescent Illuminator</td>
 </tr>
 <tr>
 <td>Microscope Platform</td>
 <td>Siskiyou</td>
 <td>Custom assembled</td>
 </tr>
 <tr>
 <td>RC-22 Submersible recording chamber (Product # 64-0228)</td>
 <td>Warner Instruments (WI)</td>
 <td>Requires P-1 platform and stage adaptor (Product # 64-0277 From Warner)</td>
 </tr>
 <tr>
 <td>TC2BIP 2/3Ch Temperature controller </td>
 <td>Cell Microcontrols</td>
 <td>TC2BIP 2/3Ch Temperature controller </td>
 </tr>
 <tr>
 <td>4 Axis Manual Miniature manipulator</td>
 <td>Siskiyou</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Platinum Iridium Wire (0.002 in) 
 (item # PTT0203)</td>
 <td>WPI</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>A365 Stimulus Isolator</td>
 <td>WPI</td>
 <td>A365 Stimulus Isolator</td>
 </tr>
 <tr>
 <td>Multiclamp 700b Amplifier</td>
 <td>Axon Instruments</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Digidata 1322A A/D converter</td>
 <td>Axon Instruments</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>PClamp software</td>
 <td>Axon Instruments</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Personal Computer (Pentium 4)</td>
 <td>Dell</td>
 <td>&nbsp;</td>
 </tr>
</tbody>
</table>
Table 3. Electrophysiology equipment and materials

preparation of acute hippocampal slices from rats and transgenic mice for the study of synaptic alterations during aging and amyloid pathology

The rodent hippocampal slice preparation is perhaps the most broadly used tool for investigating mammalian synaptic function and plasticity. The hippocampus can be extracted quickly and easily from rats and mice and slices remain viable for hours in oxygenated artificial cerebrospinal fluid. Moreover, basic electrophysisologic techniques are easily applied to the investigation of synaptic function in hippocampal slices and have provided some of the best biomarkers for cognitive impairments. The hippocampal slice is especially popular for the study of synaptic plasticity mechanisms involved in learning and memory. Changes in the induction of long-term potentiation and depression (LTP and LTD) of synaptic efficacy in hippocampal slices (or lack thereof) are frequently used to describe the neurologic phenotype of cognitively-impaired animals and/or to evaluate the mechanism of action of nootropic compounds. This article outlines the procedures we use for preparing hippocampal slices from rats and transgenic mice for the study of synaptic alterations associated with brain aging and Alzheimer's disease (AD)1-3. Use of aged rats and AD model mice can present a unique set of challenges to researchers accustomed to using younger rats and/or mice in their research. Aged rats have thicker skulls and tougher connective tissue than younger rats and mice, which can delay brain extraction and/or dissection and consequently negate or exaggerate real age-differences in synaptic function and plasticity. Aging and amyloid pathology may also exacerbate hippocampal damage sustained during the dissection procedure, again complicating any inferences drawn from physiologic assessment. Here, we discuss the steps taken during the dissection procedure to minimize these problems. Examples of synaptic responses acquired in "healthy" and "unhealthy" slices from rats and mice are provided, as well as representative synaptic plasticity experiments. The possible impact of other methodological factors on synaptic function in these animal models (e.g. recording solution components, stimulation parameters) are also discussed. While the focus of this article is on the use of aged rats and transgenic mice, novices to slice physiology should find enough detail here to get started on their own studies, using a variety of rodent models.

Watch this Scientific Journal Video about Preparation of Acute Hippocampal Slices from Rats and Transgenic Mice for the Study of Synaptic Alterations during Aging and Amyloid Pathology at JoVE.com

Preparation of Acute Hippocampal Slices from Rats and Transgenic Mice for the Study of Synaptic Alterations during Aging and Amyloid Pathology

This article outlines procedures for preparing hippocampal slices from rats and transgenic mice for the study of synaptic alterations associated with brain aging and age-related neurodegenerative diseases, such as Alzheimer&#x2019;s disease.

The rodent hippocampal slice preparation is perhaps the most broadly used tool for investigating mammalian synaptic function and plasticity. The ...

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93.7K Views.  University of Kentucky College of Public Health. This article outlines procedures for preparing hippocampal slices from rats and transgenic mice for the study of synaptic alterations associated with brain aging and age-related neurodegenerative diseases, such as Alzheimer’s disease.

Video: Preparation of Acute Hippocampal Slices from Rats and Transgenic Mice for the Study of Synaptic Alterations during Aging and Amyloid Pathology

Preparation of Oligomeric &beta;-amyloid1-42 and Induction of Synaptic Plasticity Impairment on Hippocampal Slices

Impairment of synaptic connections is likely to underlie the subtle amnesic changes occurring at the early stages of Alzheimer s Disease (AD). &beta;-amyloid (A&beta;), a peptide produced in high amounts in AD, is known to reduce Long-Term Potentiation (LTP), a cellular correlate of learning and memory. Indeed, LTP impairment caused by A&beta; is a useful experimental paradigm for studying synaptic dysfunctions in AD models and for screening drugs capable of mitigating or reverting such synaptic impairments. Studies have shown that A&beta; produces the LTP disruption preferentially via its oligomeric form. Here we provide a detailed protocol for impairing LTP by perfusion of oligomerized synthetic A&beta;1-42 peptide onto acute hippocampal slices. In this video, we outline a step-by-step procedure for the preparation of oligomeric A&beta;1-42. Then, we follow an individual experiment in which LTP is reduced in hippocampal slices exposed to oligomerized A&beta;1-42 compared to slices in a control experiment where no A&beta;1-42 exposure had occurred.

Preparation of Oligomeric &amp;#946;-amyloid1-42 and Induction of Synaptic Plasticity Impairment on Hippocampal Slices

One feature of Alzheimer's Disease is the elevation of A&beta;1-42 peptide. Here we provide a protocol for preparing synthetic A&beta;1-42 oligomers, which impairs hippocampal Long-Term Potentiation, a cellular correlate of memory. This procedure is useful for investigating mechanisms of A&beta;-induced pathology and drug screening.

Impairment of synaptic connections is likely to underlie the subtle amnesic changes occurring at the early stages of Alzheimer s Disease (AD). ...

Vibrodissociation of Neurons from Rodent Brain Slices to Study Synaptic Transmission and Image Presynaptic Terminals

Mechanical dissociation of neurons from the central nervous system has the advantage that presynaptic boutons remain attached to the isolated neuron of interest. This allows for examination of synaptic transmission under conditions where the extracellular and postsynaptic intracellular environments can be well controlled. A vibration-based technique without the use of proteases, known as vibrodissociation, is the most popular technique for mechanical isolation. A micropipette, with the tip fire-polished to the shape of a small ball, is placed into a brain slice made from a P1-P21 rodent. The micropipette is vibrated parallel to the slice surface and lowered through the slice thickness resulting in the liberation of isolated neurons. The isolated neurons are ready for study within a few minutes of vibrodissociation. This technique has advantages over the use of primary neuronal cultures, brain slices and enzymatically isolated neurons including: rapid production of viable, relatively mature neurons suitable for electrophysiological and imaging studies; superior control of the extracellular environment free from the influence of neighboring cells; suitability for well-controlled pharmacological experiments using rapid drug application and total cell superfusion; and improved space-clamp in whole-cell recordings relative to neurons in slice or cell culture preparations. This preparation can be used to examine synaptic physiology, pharmacology, modulation and plasticity. Real-time imaging of both pre- and postsynaptic elements in the living cells and boutons is also possible using vibrodissociated neurons. Characterization of the molecular constituents of pre- and postsynaptic elements can also be achieved with immunological and imaging-based approaches.

This report demonstrates a technique for mechanical isolation of individual viable neurons retaining attached presynaptic boutons. Vibrodissociated neurons have the advantages of rapid production, excellent pharmacological control and improved space-clamp without influence from neighboring cells. This method can be used for imaging of synaptic elements and patch-clamp recording.

Mechanical dissociation of neurons from the central nervous system has the advantage that presynaptic boutons remain attached to the isolated neuron of ...

Preparation of Acute Subventricular Zone Slices for Calcium Imaging

The subventricular zone (SVZ) is one of the two neurogenic zones in the postnatal brain. The SVZ contains densely packed cells, including neural progenitor cells with astrocytic features (called SVZ astrocytes), neuroblasts, and intermediate progenitor cells. Neuroblasts born in the SVZ tangentially migrate a great distance to the olfactory bulb, where they differentiate into interneurons. Intercellular signaling through adhesion molecules and diffusible signals play important roles in controlling neurogenesis. Many of these signals trigger intercellular calcium activity that transmits information inside and between cells. Calcium activity is thus reflective of the activity of extracellular signals and is an optimal way to understand functional intercellular signaling among SVZ cells.
Calcium activity has been studied in many other regions and cell types, including mature astrocytes and neurons. However, the traditional method to load cells with calcium indicator dye (i.e. bath loading) was not efficient at loading all SVZ cell types. Indeed, the cellular density in the SVZ precludes dye diffusion inside the tissue. In addition, preparing sagittal slices will better preserve the three-dimensional arrangement of SVZ cells, particularly the stream of neuroblast migration on the rostral-caudal axis.
Here, we describe methods to prepare sagittal sections containing the SVZ, the loading of SVZ cells with calcium indicator dye, and the acquisition of calcium activity with time-lapse movies. We used Fluo-4 AM dye for loading SVZ astrocytes using pressure application inside the tissue. Calcium activity was recorded using a scanning confocal microscope allowing a precise resolution for distinguishing individual cells. Our approach is applicable to other neurogenic zones including the adult hippocampal subgranular zone and embryonic neurogenic zones. In addition, other types of dyes can be applied using the described method.

A method to load subventricular zone (SVZ) cells with calcium indicator dyes for recording calcium activity is described. The postnatal SVZ contains tightly packed cells including neural progenitor cells and neuroblasts. Rather than using bath loading we injected the dye by pressure inside the tissue allowing better dye diffusion.

The subventricular zone (SVZ) is one of the two neurogenic zones in the postnatal brain. The SVZ contains densely packed cells, including neural ...

Dual Electrophysiological Recordings of Synaptically-evoked Astroglial and Neuronal Responses in Acute Hippocampal Slices

Astrocytes form together with neurons tripartite synapses, where they integrate and modulate neuronal activity. Indeed, astrocytes sense neuronal inputs through activation of their ion channels and neurotransmitter receptors, and process information in part through activity-dependent release of gliotransmitters. Furthermore, astrocytes constitute the main uptake system for glutamate, contribute to potassium spatial buffering, as well as to GABA clearance. These cells therefore constantly monitor synaptic activity, and are thereby sensitive indicators for alterations in synaptically-released glutamate, GABA and extracellular potassium levels. Additionally, alterations in astroglial uptake activity or buffering capacity can have severe effects on neuronal functions, and might be overlooked when characterizing physiopathological situations or knockout mice. Dual recording of neuronal and astroglial activities is therefore an important method to study alterations in synaptic strength associated to concomitant changes in astroglial uptake and buffering capacities. Here we describe how to prepare hippocampal slices, how to identify stratum radiatum astrocytes, and how to record simultaneously neuronal and astroglial electrophysiological responses. Furthermore, we describe how to isolate pharmacologically the synaptically-evoked astroglial currents.

The preparation of acute brain slices from isolated hippocampi, as well as the simultaneous electrophysiological recordings of astrocytes and neurons in stratum radiatum during stimulation of schaffer collaterals is described. The pharmacological isolation of astroglial potassium and glutamate transporter currents is demonstrated.

Astrocytes form together with neurons tripartite synapses, where they integrate and modulate neuronal activity. Indeed, astrocytes sense neuronal inputs ...

Stereotaxic Infusion of Oligomeric Amyloid-beta into the Mouse Hippocampus

Alzheimer&#8217;s disease is a neurodegenerative disease affecting the aging population. A key neuropathological feature of the disease is the over-production of amyloid-beta and the deposition of amyloid-beta plaques in brain regions of the afflicted individuals. Throughout the years scientists have generated numerous Alzheimer&#8217;s disease mouse models that attempt to replicate the amyloid-beta pathology. Unfortunately, the mouse models only selectively mimic the disease features. Neuronal death, a prominent effect in the brains of Alzheimer&#8217;s disease patients, is noticeably lacking in these mice. Hence, we and others have employed a method of directly infusing soluble oligomeric species of amyloid-beta - forms of amyloid-beta that have been proven to be most toxic to neurons - stereotaxically into the brain. In this report we utilize male C57BL/6J mice to document this surgical technique of increasing amyloid-beta levels in a select brain region. The infusion target is the dentate gyrus of the hippocampus because this brain structure, along with the basal forebrain that is connected by the cholinergic circuit, represents one of the areas of degeneration in the disease. The results of elevating amyloid-beta in the dentate gyrus via stereotaxic infusion reveal increases in neuron loss in the dentate gyrus within 1 week, while there is a concomitant increase in cell death and cholinergic neuron loss in the vertical limb of the diagonal band of Broca of the basal forebrain. These effects are observed up to 2 weeks. Our data suggests that the current amyloid-beta infusion model provides an alternative mouse model to address region specific neuron death in a short-term basis. The advantage of this model is that amyloid-beta can be elevated in a spatial and temporal manner.

Here, we present a protocol for direct stereotaxic brain infusion of amyloid-beta. This methodology provides an alternative in vivo mouse model to address the short-term effects of amyloid-beta on brain neurons.

Alzheimer&#8217;s disease is a neurodegenerative disease affecting the aging population. A key neuropathological feature of the disease is the ...

Investigation of Synaptic Tagging/Capture and Cross-capture using Acute Hippocampal Slices from Rodents

Synaptic tagging and capture (STC) and cross-tagging are two important mechanisms at cellular level that explain how synapse-specificity and associativity is achieved in neurons within a specific time frame. These long-term plasticity-related processes are the leading candidate models to study the basis of memory formation and persistence at the cellular level. Both STC and cross-tagging involve two serial processes: (1) setting of the synaptic tag as triggered by a specific pattern of stimulation, and (2) synaptic capture, whereby the synaptic tag interacts with newly synthesized plasticity-related proteins (PRPs). Much of the understanding about the concepts of STC and cross-tagging arises from the studies done in CA1 region of the hippocampus and because of the technical complexity many of the laboratories are still unable to study these processes. Experimental conditions for the preparation of hippocampal slices and the recording of stable late-LTP/LTD are extremely important to study synaptic tagging/cross-tagging. This video article describes the experimental procedures to study long-term plasticity processes such as STC and cross-tagging in the CA1 pyramidal neurons using stable, long-term field-potential recordings from acute hippocampal slices of rats.

This video article describes experimental procedures to study long-term plasticity and its associative processes such as synaptic tagging, capture and cross-tagging in the CA1 pyramidal neurons using acute hippocampal slices from rodents.

Synaptic tagging and capture (STC) and cross-tagging are two important mechanisms at cellular level that explain how synapse-specificity and associativity ...

Preparation of Acute Brain Slices Using an Optimized N-Methyl-D-glucamine Protective Recovery Method

This protocol is a practical guide to the N-methyl-D-glucamine (NMDG) protective recovery method of brain slice preparation. Numerous recent studies have validated the utility of this method for enhancing neuronal preservation and overall brain slice viability. The implementation of this technique by early adopters has facilitated detailed investigations into brain function using diverse experimental applications and spanning a wide range of animal ages, brain regions, and cell types. Steps are outlined for carrying out the protective recovery brain slice technique using an optimized NMDG artificial cerebrospinal fluid (aCSF) media formulation and enhanced procedure to reliably obtain healthy brain slices for patch clamp electrophysiology. With this updated approach, a substantial improvement is observed in the speed and reliability of gigaohm seal formation during targeted patch clamp recording experiments while maintaining excellent neuronal preservation, thereby facilitating challenging experimental applications. Representative results are provided from multi-neuron patch clamp recording experiments to assay synaptic connectivity in neocortical brain slices prepared from young adult transgenic mice and mature adult human neurosurgical specimens. Furthermore, the optimized NMDG protective recovery method of brain slicing is compatible with both juvenile and adult animals, thus resolving a limitation of the original methodology. In summary, a single media formulation and brain slicing procedure can be implemented across various species and ages to achieve excellent viability and tissue preservation.

Preparation of Acute Brain Slices Using an Optimized N-Methyl-D-glucamine Protective Recovery Method

This protocol demonstrates the implementation of an optimized N-methyl-D-glucamine (NMDG) protective recovery method of brain slice preparation. A single media formulation is used to reliably obtain healthy brain slices from animals of any age and for diverse experimental applications.

This protocol is a practical guide to the N-methyl-D-glucamine (NMDG) protective recovery method of brain slice preparation. Numerous recent studies have ...

Recording Synaptic Plasticity in Acute Hippocampal Slices Maintained in a Small-volume Recycling-, Perfusion-, and Submersion-type Chamber System

Even though experiments on brain slices have been in use since 1951, problems remain that reduce the probability of achieving a stable and successful analysis of synaptic transmission modulation when performing field potential or intracellular recordings. This manuscript describes methodological aspects that might be helpful in improving experimental conditions for the maintenance of acute brain slices and for recording field excitatory postsynaptic potentials in a commercially available submersion chamber with an outflow-carbogenation unit. The outflow-carbogenation helps to stabilize the oxygen level in experiments that rely on the recycling of a small buffer reservoir to enhance the cost-efficiency of drug experiments. In addition, the manuscript presents representative experiments that examine the effects of different carbogenation modes and stimulation paradigms on the activity-dependent synaptic plasticity of synaptic transmission.

This protocol describes the stabilization of the oxygen level in a small volume of recycled buffer and methodological aspects of recording activity-dependent synaptic plasticity in submerged acute hippocampal slices.

Even though experiments on brain slices have been in use since 1951, problems remain that reduce the probability of achieving a stable and successful ...

Single Synapse Indicators of Glutamate Release and Uptake in Acute Brain Slices from Normal and Huntington Mice

Synapses are highly compartmentalized functional units that operate independently on each other. In Huntington&#39;s disease (HD) and other neurodegenerative disorders, this independence might be compromised due to insufficient glutamate clearance and the resulting spill-in and spill-out effects. Altered astrocytic coverage of the presynaptic terminals and/or dendritic spines as well as a reduced size of glutamate transporter clusters at glutamate release sites have been implicated in the pathogenesis of diseases resulting in symptoms of dys-/hyperkinesia. However, the mechanisms leading to the dysfunction of glutamatergic synapses in HD are not well understood. Improving and applying synapse imaging we have obtained data shedding new light on the mechanisms impeding the initiation of movements. Here, we describe the principle elements of a relatively inexpensive approach to achieve single synapse resolution by using the new genetically encoded ultrafast glutamate sensor iGluu, wide-field optics, a scientific CMOS (sCMOS) camera, a 473 nm laser and a laser positioning system to evaluate the state of corticostriatal synapses in acute slices from age appropriate healthy or diseased mice. Glutamate transients were constructed from single or multiple pixels to obtain estimates of i) glutamate release based on the maximal elevation of the glutamate concentration [Glu] next to the active zone and ii) glutamate uptake as reflected in the time constant of decay (TauD) of the perisynaptic [Glu]. Differences in the resting bouton size and contrasting patterns of short-term plasticity served as criteria for the identification of corticostriatal terminals as belonging to the intratelencephalic (IT) or the pyramidal tract (PT) pathway. Using these methods, we discovered that in symptomatic HD mice ~40% of PT-type corticostriatal synapses exhibited insufficient glutamate clearance, suggesting that these synapses might be at risk to excitotoxic damage. The results underline the usefulness of TauD as a biomarker of dysfunctional synapses in Huntington mice with a hypokinetic phenotype.

We present a protocol to evaluate the balance between glutamate release and clearance at single corticostriatal glutamatergic synapses in acute slices from adult mice. This protocol uses the fluorescent sensor iGluu for glutamate detection, a sCMOS camera for signal acquisition and a device for focal laser illumination.

Synapses are highly compartmentalized functional units that operate independently on each other. In Huntington&#39;s disease (HD) and other ...

Preparation of Acute Human Hippocampal Slices for Electrophysiological Recordings

Epilepsy affects about 1% of the world population and leads to a severe decrease in quality of life due to ongoing seizures as well as high risk for sudden death. Despite an abundance of available treatment options, about 30% of patients are drug-resistant. Several novel therapeutics have been developed using animal models, though the rate of drug-resistant patients remains unaltered. One of probable reasons is the lack of translation between rodent models and humans, such as a weak representation of human pharmacoresistance in animal models. Resected human brain tissue as a preclinical evaluation tool has the advantage to bridge this translational gap. Described here is a method for high quality preparation of human hippocampal brain slices and subsequent stable induction of epileptiform activity. The protocol describes the induction of burst activity during application of 8 mM KCl and 4-aminopyridin. This activity is sensitive to established AED lacosamide or novel antiepileptic candidates, such as dimethylethanolamine (DMEA). In addition, the method describes induction of seizure-like events in CA1 of human hippocampal brain slices by reduction of extracellular Mg2+ and application of bicuculline, a GABAA receptor blocker. The experimental set-up can be used to screen potential antiepileptic substances for their effects on epileptiform activity. Furthermore, mechanisms of action postulated for specific compounds can be validated using this approach in human tissue (e.g., using patch-clamp recordings). To conclude, investigation of vital human brain tissue ex vivo (here, resected hippocampus from patients suffering from temporal lobe epilepsy) will improve the current knowledge of physiological and pathological mechanisms in the human brain.

The presented protocol describes the transport and preparation of resected human hippocampal tissue with the ultimate goal to use vital brain slices as a preclinical evaluation tool for potential antiepileptic substances.

Epilepsy affects about 1% of the world population and leads to a severe decrease in quality of life due to ongoing seizures as well as high risk for ...