This work was funded by the National Health and Medical Research Council (NHMRC) of Australia (grants 631000, 1043933, 1144638, and 1184974 to B.A.G. and R.J.C.) and the Hunter Medical Research Institute (grant to B.A.G. and R.J.C.).

<ol><li>Smith, K. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Calretinin+positive+neurons+form+an+excitatory+amplifier+network+in+the+spinal+cord+dorsal+horn%5BTitle%5D)+AND+%22eLife%22%5BJournal%5D)">Calretinin positive neurons form an excitatory amplifier network in the spinal cord dorsal horn.</a> eLife. 8, 49190(2019).</li>
<li>Smith, K. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Functional+heterogeneity+of+calretinin-expressing+neurons+in+the+mouse+superficial+dorsal+horn%3A+implications+for+spinal+pain+processing%5BTitle%5D)+AND+%22The+Journal+of+physiology%22%5BJournal%5D)">Functional heterogeneity of calretinin-expressing neurons in the mouse superficial dorsal horn: implications for spinal pain processing.</a> The Journal of physiology. 593 (19), 4319-4339 (2015).</li>
<li>Boyle, K. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Defining+a+spinal+microcircuit+that+gates+myelinated+afferent+input%3A+Implications+for+tactile+allodynia%5BTitle%5D)+AND+%22Cell+Reports%22%5BJournal%5D)">Defining a spinal microcircuit that gates myelinated afferent input: Implications for tactile allodynia.</a> Cell Reports. 28 (2), 526-540 (2019).</li>
<li>Browne, T. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Transgenic+cross-referencing+of+inhibitory+and+excitatory+interneuron+populations+to+dissect+neuronal+heterogeneity+in+the+dorsal+horn%5BTitle%5D)+AND+%22Frontiers+in+Molecular+Neuroscience%22%5BJournal%5D)">Transgenic cross-referencing of inhibitory and excitatory interneuron populations to dissect neuronal heterogeneity in the dorsal horn.</a> Frontiers in Molecular Neuroscience. 13, 32(2020).</li>
<li>Graham, B. A., Hughes, D. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Rewards%2C+perils+and+pitfalls+of+untangling+spinal+pain+circuits%5BTitle%5D)+AND+%22Current+Opinion+in+Physiology%22%5BJournal%5D)">Rewards, perils and pitfalls of untangling spinal pain circuits.</a> Current Opinion in Physiology. 11, 35-41 (2019).</li>
<li>Todd, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Neuronal+circuitry+for+pain+processing+in+the+dorsal+horn%5BTitle%5D)+AND+%22Nature+Reviews+Neuroscience%22%5BJournal%5D)">Neuronal circuitry for pain processing in the dorsal horn.</a> Nature Reviews Neuroscience. 11 (12), 823-836 (2010).</li>
<li>Hughes, D. I., Todd, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Central+nervous+system+targets%3A+inhibitory+interneurons+in+the+spinal+cord%5BTitle%5D)+AND+%22Neurotherapeutics%22%5BJournal%5D)">Central nervous system targets: inhibitory interneurons in the spinal cord.</a> Neurotherapeutics. 17 (3), 874-885 (2020).</li>
<li>Duan, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Identification+of+spinal+circuits+transmitting+and+gating+mechanical+pain%5BTitle%5D)+AND+%22Cell%22%5BJournal%5D)">Identification of spinal circuits transmitting and gating mechanical pain.</a> Cell. 159 (6), 1417-1432 (2014).</li>
<li>Hachisuka, J., Chiang, M. C., Ross, S. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Itch+and+neuropathis+itch%5BTitle%5D)+AND+%22Pain%22%5BJournal%5D)">Itch and neuropathis itch.</a> Pain. 159 (3), 603(2018).</li>
<li>Foster, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Targeted+ablation%2C+silencing%2C+and+activation+establish+glycinergic+dorsal+horn+neurons+as+key+components+of+a+spinal+gate+for+pain+and+itch%5BTitle%5D)+AND+%22Neuron%22%5BJournal%5D)">Targeted ablation, silencing, and activation establish glycinergic dorsal horn neurons as key components of a spinal gate for pain and itch.</a> Neuron. 85 (6), 1289-1304 (2015).</li>
<li>Bourane, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Identification+of+a+spinal+circuit+for+light+touch+and+fine+motor+control%5BTitle%5D)+AND+%22Cell%22%5BJournal%5D)">Identification of a spinal circuit for light touch and fine motor control.</a> Cell. 160 (3), 503-515 (2015).</li>
<li>Cheng, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Identification+of+spinal+circuits+involved+in+touch-evoked+dynamic+mechanical+pain%5BTitle%5D)+AND+%22Nature+neuroscience%22%5BJournal%5D)">Identification of spinal circuits involved in touch-evoked dynamic mechanical pain.</a> Nature neuroscience. 20 (6), 804-814 (2017).</li>
<li>Peirs, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Mechanical+allodynia+circuitry+in+the+dorsal+horn+is+defined+by+the+nature+of+the+injury%5BTitle%5D)+AND+%22Neuron%22%5BJournal%5D)">Mechanical allodynia circuitry in the dorsal horn is defined by the nature of the injury.</a> Neuron. 109 (1), 73-90 (2021).</li>
<li>Huang, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Circuit+dissection+of+the+role+of+somatostatin+in+itch+and+pain%5BTitle%5D)+AND+%22Nature+Neuroscience%22%5BJournal%5D)">Circuit dissection of the role of somatostatin in itch and pain.</a> Nature Neuroscience. 21 (5), 707-716 (2018).</li>
<li>Obien, M. E. J., Deligkaris, K., Bullmann, T., Bakkum, D. J., Frey, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Revealing+neuronal+function+through+microelectrode+array+recordings%5BTitle%5D)+AND+%22Frontiers+in+Neuroscience%22%5BJournal%5D)">Revealing neuronal function through microelectrode array recordings.</a> Frontiers in Neuroscience. 8, 423(2015).</li>
<li>Nam, Y., Wheeler, B. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((In+vitro+microelectrode+array+technology+and+neural+recordings%5BTitle%5D)+AND+%22Critical+Reviews+in+Biomedical+Engineering%22%5BJournal%5D)">In vitro microelectrode array technology and neural recordings.</a> Critical Reviews in Biomedical Engineering. 39 (1), 45-61 (2011).</li>
<li>Johnstone, A. F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Microelectrode+arrays%3A+a+physiologically+based+neurotoxicity+testing+platform+for+the+21st+century%5BTitle%5D)+AND+%22Neurotoxicology%22%5BJournal%5D)">Microelectrode arrays: a physiologically based neurotoxicity testing platform for the 21st century.</a> Neurotoxicology. 31 (4), 331-350 (2010).</li>
<li>Stett, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Biological+application+of+microelectrode+arrays+in+drug+discovery+and+basic+research%5BTitle%5D)+AND+%22Analytical+and+Bioanalytical+Chemistry%22%5BJournal%5D)">Biological application of microelectrode arrays in drug discovery and basic research.</a> Analytical and Bioanalytical Chemistry. 377 (3), 486-495 (2003).</li>
<li>Xu, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Trends+and+recent+development+of+the+microelectrode+arrays+%28MEAs%29%5BTitle%5D)+AND+%22Biosensors+and+Bioelectronics%22%5BJournal%5D)">Trends and recent development of the microelectrode arrays (MEAs).</a> Biosensors and Bioelectronics. 175 (1), 112854(2020).</li>
<li>Chapman, R. J., Cilia La Corte, P. F., Asghar, A. U. R., King, A. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Network-based+activity+induced+by+4-aminopyridine+in+rat+dorsal+horn+in+vitro+is+mediated+by+both+chemical+and+electrical+synapses%5BTitle%5D)+AND+%22The+Journal+of+Physiology%22%5BJournal%5D)">Network-based activity induced by 4-aminopyridine in rat dorsal horn in vitro is mediated by both chemical and electrical synapses.</a> The Journal of Physiology. 587, Pt 11 2499-2510 (2009).</li>
<li>Ruscheweyh, R., Sandkühler, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Epileptiform+activity+in+rat+spinal+dorsal+horn+in+vitro+has+common+features+with+neuropathic+pain%5BTitle%5D)+AND+%22Pain%22%5BJournal%5D)">Epileptiform activity in rat spinal dorsal horn in vitro has common features with neuropathic pain.</a> Pain. 105 (1-2), 327-338 (2003).</li>
<li>Kay, C. W., Ursu, D., Sher, E., King, A. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+role+of+Cx36+and+Cx43+in+4-aminopyridine-induced+rhythmic+activity+in+the+spinal+nociceptive+dorsal+horn%3A+an+electrophysiological+study+in+vitro%5BTitle%5D)+AND+%22Physiological+Reports%22%5BJournal%5D)">The role of Cx36 and Cx43 in 4-aminopyridine-induced rhythmic activity in the spinal nociceptive dorsal horn: an electrophysiological study in vitro.</a> Physiological Reports. 4 (14), 12852(2016).</li>
<li>Jankowska, E., Lundberg, A., Rudomin, P., Sykova, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Effects+of+4-aminopyridine+on+synaptic+transmission+in+the+cat+spinal+cord%5BTitle%5D)+AND+%22Brain+Research%22%5BJournal%5D)">Effects of 4-aminopyridine on synaptic transmission in the cat spinal cord.</a> Brain Research. 240 (1), 117-129 (1982).</li>
<li>Semba, K., Geller, H. M., Egger, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((4-Aminopyridine+induces+expansion+of+cutaneous+receptive+fields+of+dorsal+horn+cells%5BTitle%5D)+AND+%22Brain+Research%22%5BJournal%5D)">4-Aminopyridine induces expansion of cutaneous receptive fields of dorsal horn cells.</a> Brain Research. 343 (2), 398-402 (1985).</li>
<li>Ruscheweyh, R., Sandkühler, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Long-range+oscillatory+Ca2%2B+waves+in+rat+spinal+dorsal+horn%5BTitle%5D)+AND+%22European+Journal+of+Neuroscience%22%5BJournal%5D)">Long-range oscillatory Ca2+ waves in rat spinal dorsal horn.</a> European Journal of Neuroscience. 22 (8), 1967-1976 (2005).</li>
<li>Egert, U., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+novel+organotypic+long-term+culture+of+the+rat+hippocampus+on+substrate-integrated+multielectrode+arrays%5BTitle%5D)+AND+%22Brain+Research+Protocols%22%5BJournal%5D)">A novel organotypic long-term culture of the rat hippocampus on substrate-integrated multielectrode arrays.</a> Brain Research Protocols. 2 (4), 229-242 (1998).</li>
<li>Thiebaud, P., De Rooij, N., Koudelka-Hep, M., Stoppini, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Microelectrode+arrays+for+electrophysiological+monitoring+of+hippocampal+organotypic+slice+cultures%5BTitle%5D)+AND+%22IEEE+Transactions+on+Biomedical+Engineering%22%5BJournal%5D)">Microelectrode arrays for electrophysiological monitoring of hippocampal organotypic slice cultures.</a> IEEE Transactions on Biomedical Engineering. 44 (11), 1159-1163 (1997).</li>
<li>Rey, H. G., Pedreira, C., Quiroga, R. Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Past%2C+present+and+future+of+spike+sorting+techniques%5BTitle%5D)+AND+%22Brain+Research+Bulletin%22%5BJournal%5D)">Past, present and future of spike sorting techniques.</a> Brain Research Bulletin. 119, 106-117 (2015).</li>
<li>Satuvuori, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Measures+of+spike+train+synchrony+for+data+with+multiple+time+scales%5BTitle%5D)+AND+%22Journal+of+Neuroscience+Methods%22%5BJournal%5D)">Measures of spike train synchrony for data with multiple time scales.</a> Journal of Neuroscience Methods. 287, 25-38 (2017).</li>
<li>Mendis, G. D. C., Morrisroe, E., Reid, C. A., Halgamuge, S. K., Petrou, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Use+of+local+field+potentials+of+dissociated+cultures+grown+on+multi-electrode+arrays+for+pharmacological+assays%5BTitle%5D)+AND+%2238th+Annual+International+Conference+of+the+IEEE+Engineering+in+Medicine+and+Biology+Society%22%5BJournal%5D)">Use of local field potentials of dissociated cultures grown on multi-electrode arrays for pharmacological assays.</a> 38th Annual International Conference of the IEEE Engineering in Medicine and Biology Society. , 952-956 (2016).</li>
<li>Hughes, D. I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Morphological%2C+neurochemical+and+electrophysiological+features+of+parvalbumin-expressing+cells%3A+a+likely+source+of+axo-axonic+inputs+in+the+mouse+spinal+dorsal+horn%5BTitle%5D)+AND+%22The+Journal+of+Physiology%22%5BJournal%5D)">Morphological, neurochemical and electrophysiological features of parvalbumin-expressing cells: a likely source of axo-axonic inputs in the mouse spinal dorsal horn.</a> The Journal of Physiology. 590 (16), 3927-3951 (2012).</li>
<li>Peirs, C., Seal, R. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Neural+circuits+for+pain%3A+recent+advances+and+current+views%5BTitle%5D)+AND+%22Science%22%5BJournal%5D)">Neural circuits for pain: recent advances and current views.</a> Science. 354 (6312), 578-584 (2016).</li>
<li>Li, J., Baccei, M. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Developmental+regulation+of+membrane+excitability+in+rat+spinal+lamina+I+projection+neurons%5BTitle%5D)+AND+%22Journal+of+Neurophysiology%22%5BJournal%5D)">Developmental regulation of membrane excitability in rat spinal lamina I projection neurons.</a> Journal of Neurophysiology. 107 (10), 2604-2614 (2012).</li>
<li>Li, J., Baccei, M. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Pacemaker+neurons+within+newborn+spinal+pain+circuits%5BTitle%5D)+AND+%22Journal+of+Neuroscience%22%5BJournal%5D)">Pacemaker neurons within newborn spinal pain circuits.</a> Journal of Neuroscience. 31 (24), 9010-9022 (2011).</li>
<li>Sandkühler, J., Eblen-Zajjur, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Identification+and+characterization+of+rhythmic+nociceptive+and+non-nociceptive+spinal+dorsal+horn+neurons+in+the+rat%5BTitle%5D)+AND+%22Neuroscience%22%5BJournal%5D)">Identification and characterization of rhythmic nociceptive and non-nociceptive spinal dorsal horn neurons in the rat.</a> Neuroscience. 61 (4), 991-1006 (1994).</li>
<li>Lucas-Romero, J., Rivera-Arconada, I., Roza, C., Lopez-Garcia, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Origin+and+classification+of+spontaneous+discharges+in+mouse+superficial+dorsal+horn+neurons%5BTitle%5D)+AND+%22Scientific+Reports%22%5BJournal%5D)">Origin and classification of spontaneous discharges in mouse superficial dorsal horn neurons.</a> Scientific Reports. 8 (1), 9735-9735 (2018).</li>
<li>Antonio, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((L.+al.+In+vitro+seizure+like+events+and+changes+in+ionic+concentration%5BTitle%5D)+AND+%22Journal+of+Neuroscience+Methods%22%5BJournal%5D)">L. al. In vitro seizure like events and changes in ionic concentration.</a> Journal of Neuroscience Methods. 260, 33-44 (2016).</li>
<li>Avoli, M., Jefferys, J. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Models+of+drug-induced+epileptiform+synchronization+in+vitro%5BTitle%5D)+AND+%22Journal+of+Neuroscience+Methods%22%5BJournal%5D)">Models of drug-induced epileptiform synchronization in vitro.</a> Journal of Neuroscience Methods. 260, 26-32 (2016).</li>
<li>Taccola, G., Nistri, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Low+micromolar+concentrations+of+4-aminopyridine+facilitate+fictive+locomotion+expressed+by+the+rat+spinal+cord+in+vitro%5BTitle%5D)+AND+%22Neuroscience%22%5BJournal%5D)">Low micromolar concentrations of 4-aminopyridine facilitate fictive locomotion expressed by the rat spinal cord in vitro.</a> Neuroscience. 126 (2), 511-520 (2004).</li>
<li>Mitra, P., Brownstone, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((An+in+vitro+spinal+cord+slice+preparation+for+recording+from+lumbar+motoneurons+of+the+adult+mouse%5BTitle%5D)+AND+%22Journal+of+Neurophysiology%22%5BJournal%5D)">An in vitro spinal cord slice preparation for recording from lumbar motoneurons of the adult mouse.</a> Journal of Neurophysiology. 107 (2), 728-741 (2012).</li>
<li>Egert, U., Heck, D., Aertsen, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Two-dimensional+monitoring+of+spiking+networks+in+acute+brain+slices%5BTitle%5D)+AND+%22Experimental+Brain+Research%22%5BJournal%5D)">Two-dimensional monitoring of spiking networks in acute brain slices.</a> Experimental Brain Research. 142 (2), 268-274 (2002).</li>
</ol>

The authors have no conflicts of interest to declare.

Despite the importance of the spinal DH in nociceptive signaling, processing, and the resulting behavioral and emotional responses that characterize pain, the circuits within this region remain poorly understood. A key challenge in investigating this issue has been the diversity of neuron populations that comprise these circuits6,31,32. Recent advances in transgenic technologies, led by optogenetics and chemogenetics, are beginn...

The roles of specific types of inhibitory and excitatory interneurons within the spinal cord DH are being uncovered at a rapid rate1,2,3,4. Together, interneurons make up over 95% of the neurons in the DH and are involved in sensory processing, including nociception. Furthermore, these interneuron circuits are important for determining whether peripheral signals ascend the neuroaxis to reach the brain and contribute to the perception of pain5,6,7. To date, most studies have investigated the role of DH neurons at either the single-cell or whole-organism level of analysis using combinations of in vitro intracellular electrophysiology, neuroanatomical labeling, and in vivo behavioral analysis1,3,8,9,10,11,12,13,14. These approaches have significantly advanced the understanding of the role of specific neuron populations in pain processing. However, a gap remains in understanding how specific cell types and small macro-circuits influence large populations of neurons at a microcircuit level to subsequently shape the output of the DH, behavioral responses, and the pain experience.
One technology that can investigate macro-circuit or multicellular-level function is the microelectrode array (MEA)15,16. MEAs have been used to investigate nervous system function for several decades17,18. In the brain, they have facilitated the study of neuronal development, synaptic plasticity, pharmacological screening, and toxicity testing17,18. They can be used for both in vitro and in vivo applications, depending on the type of MEA. Furthermore, the development of MEAs has evolved rapidly, with different electrode numbers and configurations now available19. A key advantage of MEAs is their capacity to simultaneously assess electrical activity in many neurons with high spatial and temporal accuracy via multiple electrodes15,16. This provides a broader readout of how neurons interact in circuits and networks, under control conditions and in the presence of locally applied compounds.
One challenge of in vitro DH preparations is that ongoing activity levels are typically low. Here, this challenge is addressed in spinal cord DH circuits using the voltage-gated K+ channel blocker, 4-aminopryidine (4-AP), to chemically stimulate DH circuits. This drug has previously been used to establish rhythmic synchronous electrical activity in the DH of acute spinal cord slices and under acute in vivo conditions20,21,22,23,24. These experiments have used single-cell patch and extracellular recording or calcium imaging to characterize 4-AP-induced activity20,21,22,23,24,25. Together, this work has demonstrated the requirement of excitatory and inhibitory synaptic transmission and electrical synapses for rhythmic 4-AP-induced activity. Thus, the 4-AP response has been viewed as an approach that unmasks native polysynaptic DH circuits with biological relevance rather than as a drug-induced epiphenomenon. Furthermore, 4-AP-induced activity exhibits a similar response profile to analgesic and antiepileptic drugs as neuropathic pain conditions and has been used to propose novel spinally-based analgesic drug targets such as connexins20,21,22.
Here, a preparation that combines MEAs and chemical activation of the spinal DH with 4-AP to study this nociceptive circuitry at the macro-circuit, or network level of analysis, is described. This approach provides a stable and reproducible platform for investigating nociceptive circuits under naive and neuropathic &#39;pain-like&#39; conditions. This preparation is also readily applicable to test the circuit-level action of known analgesics and to screen novel analgesics in the hyperactive spinal cord.

<table><tbody><tr><td>4-aminopyridine</td><td>Sigma-Aldrich</td><td>275875-5G</td><td></td></tr><tr><td>100% ethanol</td><td>Thermo Fisher</td><td>AJA214-2.5LPL</td><td></td></tr><tr><td>CaCl&lt;sub&gt;2&lt;/sub&gt; 1M</td><td>Banksia Scientific</td><td>0430/1L</td><td></td></tr><tr><td>Carbonox (Carbogen - 95% O&lt;sub&gt;2&lt;/sub&gt;, 5% CO&lt;sub&gt;2&lt;/sub&gt;)</td><td>Coregas</td><td>219122</td><td></td></tr><tr><td>Curved long handle spring scissors</td><td>Fine Science Tools</td><td>15015-11</td><td></td></tr><tr><td>Custom made air interface incubation chamber</td><td></td><td></td><td></td></tr><tr><td>Foetal bovine serum</td><td>Thermo Fisher</td><td>10091130</td><td></td></tr><tr><td>Forceps Dumont #5</td><td>Fine Science Tools</td><td>11251-30</td><td></td></tr><tr><td>Glucose</td><td>Thermo Fisher</td><td>AJA783-500G</td><td></td></tr><tr><td>Horse serum</td><td>Thermo Fisher</td><td>16050130</td><td></td></tr><tr><td>Inverted microscope</td><td>Zeiss</td><td>Axiovert10</td><td></td></tr><tr><td>KCl</td><td>Thermo Fisher</td><td>AJA383-500G</td><td></td></tr><tr><td>Ketamine</td><td>Ceva</td><td>KETALAB04</td><td></td></tr><tr><td>Large surgical scissors</td><td>Fine Science Tools</td><td>14007-14</td><td></td></tr><tr><td>Loctite 454 Instant Adhesive</td><td>Bolts and Industrial Supplies</td><td>L4543G</td><td></td></tr><tr><td>MATLAB</td><td>MathWorks</td><td></td><td>R2018b</td></tr><tr><td>MEAs, 3-Dimensional</td><td>Multichannel Systems</td><td>60-3DMEA100/12/40iR-Ti, 60-3DMEA200/12/50iR-Ti</td><td>60 titanium nitride (TiN) electrodes with 1 internal reference electrode, organised in an 8x8 square grid. Electrodes are 12 &amp;micro;m in diameter, 40 &amp;micro;m (100/12/40) or 50 &amp;micro;m (200/12/50) high and equidistantly spaced 100 &amp;micro;m (100/12/40) or 200 &amp;micro;m (200/12/50) apart.</td></tr><tr><td>MEA headstage</td><td>Multichannel Systems</td><td>MEA2100-HS60</td><td></td></tr><tr><td>MEA interface board</td><td>Multichannel Systems</td><td>MCS-IFB 3.0 Multiboot</td><td></td></tr><tr><td>MEA net</td><td>Multichannel Systems</td><td>ALA HSG-MEA-5BD</td><td></td></tr><tr><td>MEA perfusion system</td><td>Multichannel Systems</td><td>PPS2</td><td></td></tr><tr><td>MEAs, Planar</td><td>Multichannel Systems</td><td>60MEA200/30iR-Ti, 60MEA500/30iR-Ti</td><td>60 titanium nitride (TiN) electrodes with 1 internal reference electrode, organised in either a 8x8 square grid (200/30) or a 6x10 rectangular grid (500/30). Electrodes are 30 &amp;micro;m in diameter and equidistantly spaced 200 &amp;micro;m (200/30) or 500 &amp;micro;m (500/30) apart.</td></tr><tr><td>MgCl&lt;sub&gt;2&lt;/sub&gt;</td><td>Thermo Fisher</td><td>AJA296-500G</td><td></td></tr><tr><td>Microscope camera</td><td>Motic</td><td>Moticam X Wi-Fi</td><td></td></tr><tr><td>Multi Channel Analyser software</td><td>Multichannel Systems</td><td></td><td>V 2.17.4</td></tr><tr><td>Multi Channel Experimenter software</td><td>Multichannel Systems</td><td></td><td>V 2.17.4</td></tr><tr><td>NaCl</td><td>Thermo Fisher</td><td>AJA465-500G</td><td></td></tr><tr><td>NaHCO&lt;sub&gt;3&lt;/sub&gt;</td><td>Thermo Fisher</td><td>AJA475-500G</td><td></td></tr><tr><td>NaH&lt;sub&gt;2&lt;/sub&gt;PO&lt;sub&gt;4&lt;/sub&gt;</td><td>Thermo Fisher</td><td>ACR207805000</td><td></td></tr><tr><td>Rongeurs</td><td>Fine Science Tools</td><td>16021-14</td><td></td></tr><tr><td>Small spring scissors</td><td>Fine Science Tools</td><td>91500-09</td><td></td></tr><tr><td>Small surgical scissors</td><td>Fine Science Tools</td><td>14060-09</td><td></td></tr><tr><td>Sucrose</td><td>Thermo Fisher</td><td>AJA530-500G</td><td></td></tr><tr><td>Superglue</td><td></td><td></td><td>cyanoacrylate adhesive</td></tr><tr><td>Tetrodotoxin</td><td>Abcam</td><td>AB120055</td><td></td></tr><tr><td>Vibration isolation table</td><td>Newport</td><td>VH3048W-OPT</td><td></td></tr><tr><td>Vibrating microtome</td><td>Leica</td><td>VT1200 S</td><td></td></tr></tbody></table>

recording network activity in spinal nociceptive circuits using microelectrode arrays

The roles and connectivity of specific types of neurons within the spinal cord dorsal horn (DH) are being delineated at a rapid rate to provide an increasingly detailed view of the circuits underpinning spinal pain processing. However, the effects of these connections for broader network activity in the DH remain less well understood because most studies focus on the activity of single neurons and small microcircuits. Alternatively, the use of microelectrode arrays (MEAs), which can monitor electrical activity across many cells, provides high spatial and temporal resolution of neural activity. Here, the use of MEAs with mouse spinal cord slices to study DH activity induced by chemically stimulating DH circuits with 4-aminopyridine (4-AP) is described. The resulting rhythmic activity is restricted to the superficial DH, stable over time, blocked by tetrodotoxin, and can be investigated in different slice orientations. Together, this preparation provides a platform to investigate DH circuit activity in tissue from na&#239;ve animals, animal models of chronic pain, and mice with genetically altered nociceptive function. Furthermore, MEA recordings in 4-AP-stimulated spinal cord slices can be used as a rapid screening tool to assess the capacity of novel antinociceptive compounds to disrupt activity in the spinal cord DH.

Model of network activity in the spinal cord dorsal horn 
Application of 4-AP reliably induces synchronous rhythmic activity in the spinal cord DH. Such activity presents as increased EAPs and LFPs. The later signal is a low-frequency waveform, which has previously been described in MEA recordings30. Changes in EAP and/or LFP activity following drug application reflect altered neural activity. Examples of EAPs and LFPs are shown in Figure 3B and ...

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Recording Network Activity in Spinal Nociceptive Circuits Using Microelectrode Arrays

The combined use of microelectrode array technology and 4-aminopyridine-induced chemical stimulation for investigating network-level nociceptive activity in the spinal cord dorsal horn is outlined.

The roles and connectivity of specific types of neurons within the spinal cord dorsal horn (DH) are being delineated at a rapid rate to provide an ...

recording-network-activity-spinal-nociceptive-circuits-using

Research

JoVE Journal

Neuroscience

2.8K Views.  University of Newcastle. De MEA 4-AP spinale plakvoorbereiding die aan u wordt beschreven, biedt een platform om de connectiviteit van dorsale hoorncircuits te bestuderen en hoe deze netwerken interageren tijdens spinale sensorische verwerking. De gepresenteerde methodologie maakt het mogelijk om de activiteit van het dorsale hoorncircuit te onderzoeken op een macroscopisch regionaal resolutieniveau. Deze voorbereiding kan worden gebruikt als een snelle screening om het vermogen van verbindingen om de signalering in ...

Video: Recording Network Activity in Spinal Nociceptive Circuits Using Microelectrode Arrays

Simultaneous Recordings of Cortical Local Field Potentials and Electrocorticograms in Response to Nociceptive Laser Stimuli from Freely Moving Rats

Electrocortical responses, elicited by laser heat pulses that selectively activate nociceptive free nerve endings, are widely used in many animal and human studies to investigate the cortical processing of nociceptive information. These laser-evoked brain potentials (LEPs) consist of several transient responses that are time-locked to the onset of laser stimuli. However, the functional properties of the LEP responses are still largely unknown, due to the lack of a sampling technique that can simultaneously record neural activities at the surface of the cortex (i.e., electrocorticogram [ECoG] and scalp electroencephalogram [scalp EEG]) and inside the brain (i.e., local field potential [LFP]). To address this issue, we present here an animal protocol using freely moving rats. This protocol is composed of three main procedures: (1) animal preparation and surgical procedures, (2) a simultaneous recording of ECoG and LFP in response to nociceptive laser stimuli, and (3) data analysis and feature extraction. Specifically, with the help of a 3D-printed protective shell, both ECoG and LFP electrodes implanted on the rat&#39;s skull were securely held together. During data collection, laser pulses were delivered on the rat&#39;s forepaws through gaps in the bottom of the chamber when the animal was in spontaneous stillness. Ongoing white noise was played to avoid the activation of the auditory system by the laser-generated ultrasounds. As a consequence, only nociceptive responses were selectively recorded. Using the standard analytical procedures (e.g., band-pass filtering, epoch extraction, and baseline correction) to extract stimulus-related brain responses, we obtained results showing that LEPs with a high signal-to-noise ratio were simultaneously recorded from ECoG and LFP electrodes. This methodology makes the simultaneous recording of ECoG and LFP activities possible, which provides a bridge of electrocortical signals at the mesoscopic and macroscopic levels, thereby facilitating the investigation of nociceptive information processing in the brain.

We developed a technique that simultaneously records both electrocorticography and local field potentials in response to nociceptive laser stimuli from freely moving rats. This technique helps establish a direct relationship of electrocortical signals at the mesoscopic and macroscopic levels, which facilitates the investigation of nociceptive information processing in the brain.

Electrocortical responses, elicited by laser heat pulses that selectively activate nociceptive free nerve endings, are widely used in many animal and ...

Behavior

Recording and Modulation of Epileptiform Activity in Rodent Brain Slices Coupled to Microelectrode Arrays

Temporal lobe epilepsy (TLE) is the most common partial complex epileptic syndrome and the least responsive to medications. Deep brain stimulation (DBS) is a promising approach when pharmacological treatment fails or neurosurgery is not recommended. Acute brain slices coupled to microelectrode arrays (MEAs) represent a valuable tool to study neuronal network interactions and their modulation by electrical stimulation. As compared to conventional extracellular recording techniques, they provide the added advantages of a greater number of observation points and a known inter-electrode distance, which allow studying the propagation path and speed of electrophysiological signals. However, tissue oxygenation may be greatly impaired during MEA recording, requiring a high perfusion rate, which comes at the cost of decreased signal-to-noise ratio and higher oscillations in the experimental temperature. Electrical stimulation further stresses the brain tissue, making it difficult to pursue prolonged recording/stimulation epochs. Moreover, electrical modulation of brain slice activity needs to target specific structures/pathways within the brain slice, requiring that electrode mapping be easily and quickly performed live during the experiment. Here, we illustrate how to perform the recording and electrical modulation of 4-aminopyridine (4AP)-induced epileptiform activity in rodent brain slices using planar MEAs. We show that the brain tissue obtained from mice outperforms rat brain tissue and is thus better suited for MEA experiments. This protocol guarantees the generation and maintenance of a stable epileptiform pattern that faithfully reproduces the electrophysiological features observed with conventional field potential recording, persists for several hours, and outlasts sustained electrical stimulation for prolonged epochs. Tissue viability throughout the experiment is achieved thanks to the use of a small-volume custom recording chamber allowing for laminar flow and quick solution exchange even at low (1 mL/min) perfusion rates. Quick MEA mapping for real-time monitoring and selection of stimulating electrodes is performed by a custom graphic user interface (GUI).

We illustrate how to perform recording and electrical modulation of 4-aminopyridine-induced epileptiform activity in rodent brain slices using microelectrode arrays. A custom recording chamber maintains tissue viability throughout prolonged experimental sessions. Live electrode mapping and selection of stimulating pairs are performed by a custom graphical user interface.

Temporal lobe epilepsy (TLE) is the most common partial complex epileptic syndrome and the least responsive to medications. Deep brain stimulation (DBS) ...

Use of In Vivo Single-fiber Recording and Intact Dorsal Root Ganglion with Attached Sciatic Nerve to Examine the Mechanism of Conduction Failure

Single-fiber recording has been a classical and effective electrophysiological technique over the last few decades because of its specific application for nerve fibers in the central and peripheral nervous systems. This method is particularly applicable to dorsal root ganglia (DRG), which are primary sensory neurons that exhibit a pseudo-unipolar structure of nervous processes. The patterns and features of the action potentials passed along axons are recordable in these neurons. The present study uses in vivo single-fiber recordings to observe the conduction failure of sciatic nerves in complete Freund&#8217;s adjuvant (CFA)-treated rats. As the underlying mechanism cannot be studied using in vivo single-fiber recordings, patch-clamp-recordings of DRG neurons are performed on preparations of intact DRG with the attached sciatic nerve. These recordings reveal a positive correlation between conduction failure and the rising slope of the after-hyperpolarization potential (AHP) of DRG neurons in CFA-treated animals. The protocol for in vivo single fiber-recordings allows the classification of nerve fibers via the measurement of conduction velocity and monitoring of abnormal conditions in nerve fibers in certain diseases. Intact DRG with attached peripheral nerve allows observation of the activity of DRG neurons in most physiological conditions. Conclusively, single-fiber recording combined with electrophysiological recording of intact DRGs is an effective method to examine the role of conduction failure during the analgesic process.

Single-fiber recording is an effective electrophysiological technique that is applicable to the central and peripheral nervous systems. Along with the preparation of intact DRG with the attached sciatic nerve, the mechanism of conduction failure is examined. Both protocols improve the understanding of the peripheral nervous system&#39;s relationship with pain.

Single-fiber recording has been a classical and effective electrophysiological technique over the last few decades because of its specific application for ...

In Vivo Intracellular Recording of Type-Identified Rat Spinal Motoneurons During Trans-Spinal Direct Current Stimulation

Intracellular recording of spinal motoneurons in vivo provides a &#8220;gold standard&#8221; for determining the cells&#8217; electrophysiological characteristics in the intact spinal network and holds significant advantages relative to classical in vitro or extracellular recording techniques. An advantage of in vivo intracellular recordings is that this method can be performed on adult animals with a fully mature nervous system, and therefore many observed physiological mechanisms can be translated to practical applications. In this methodological paper, we describe this procedure combined with externally applied constant current stimulation, which mimics polarization processes occurring within spinal neuronal networks. Trans-spinal direct current stimulation (tsDCS) is an innovative method increasingly used as a neuromodulatory intervention in rehabilitation after various neurological injuries as well as in sports. The influence of tsDCS on the nervous system remains poorly understood and the physiological mechanisms behind its actions are largely unknown. The application of the tsDCS simultaneously with intracellular recordings enables us to directly observe changes of motoneuron membrane properties and characteristics of rhythmic firing in response to the polarization of the spinal neuronal network, which is crucial for the understanding of tsDCS actions. Moreover, when the presented protocol includes the identification of the motoneuron with respect to an innervated muscle and its function (flexor versus extensor) as well as the physiological type (fast versus slow) it provides an opportunity to selectively investigate the influence of tsDCS on identified components of spinal circuitry, which seem to be differently affected by polarization. The presented procedure focuses on surgical preparation for intracellular recordings and stimulation with an emphasis on the steps which are necessary to achieve preparation stability and reproducibility of results. The details of the methodology of the anodal or cathodal tsDCS application are discussed while paying attention to practical and safety issues.

This protocol describes in vivo intracellular recording of rat lumbar motoneurons with simultaneous trans-spinal direct current stimulation. The method enables us to measure membrane properties and to record rhythmic firing of motoneurons before, during and after anodal or cathodal polarization of the spinal cord.

Intracellular recording of spinal motoneurons in vivo provides a &#8220;gold standard&#8221; for determining the cells&#8217; electrophysiological ...

Open-Source Real-Time Closed-Loop Electrical Threshold Tracking for Translational Pain Research

Nociceptors are a class of primary afferent neurons that signal potentially harmful noxious stimuli. An increase in nociceptor excitability occurs in acute and chronic pain conditions. This produces abnormal ongoing activity or reduced activation thresholds to noxious stimuli. Identifying the cause of this increased excitability is required for the development and validation of mechanism-based treatments. Single-neuron electrical threshold tracking can quantify nociceptor excitability. Therefore, we have developed an application to allow such measurements and demonstrate its use in humans and rodents. APTrack provides real-time data visualization and action potential identification using a temporal raster plot. Algorithms detect action potentials by threshold crossing and monitor their latency after electrical stimulation. The plugin then modulates the electrical stimulation amplitude using an up-down method to estimate the electrical threshold of the nociceptors. The software was built upon the Open Ephys system (V0.54) and coded in C++ using the JUCE framework. It runs on Windows, Linux, and Mac operating systems. The open-source code is available (<a data-saferedirecturl="https://www.google.com/url?q=https://github.com/Microneurography/APTrack&amp;source=gmail&amp;ust=1680789829274000&amp;usg=AOvVaw0nMk9J_EI2jUn8SlmC5JJm" href="https://github.com/Microneurography/APTrack" target="_blank">https://github.com/Microneurography/APTrack</a>). The electrophysiological recordings were taken from nociceptors in both a mouse skin-nerve preparation using the teased fiber method in the saphenous nerve and in healthy human volunteers using microneurography in the superficial peroneal nerve. Nociceptors were classified by their response to thermal and mechanical stimuli, as well as by monitoring the activity-dependent slowing of the conduction velocity. The software facilitated the experiment by simplifying the action potential identification through the temporal raster plot. We demonstrate real-time closed-loop electrical threshold tracking of single-neuron action potentials during&#160;in vivo&#160;human microneurography, for the first time, and during&#160;ex vivo&#160;mouse electrophysiological recordings of C-fibers and A&#948;-fibers. We establish proof of principle by showing that the electrical threshold of a human heat-sensitive C-fiber nociceptor is reduced by heating the receptive field. This plugin enables the electrical threshold tracking of single-neuron action potentials and allows the quantification of changes in nociceptor excitability.

APTrack is a software plugin developed for the Open Ephys platform that enables real-time data visualization and the closed-loop electrical threshold tracking of neuronal action potentials. We have successfully used this in microneurography for human C-fiber nociceptors and mouse C-fiber and A&#948;-fiber nociceptors.

Nociceptors are a class of primary afferent neurons that signal potentially harmful noxious stimuli. An increase in nociceptor excitability occurs in ...

Trans-Spinal Direct Current Stimulation of a Rat&#39;s Spinal Motoneuron

Source: B&#261;czyk, M., et al. <a href="https://app.jove.com/v/61439">In Vivo Intracellular Recording of Type-Identified Rat Spinal Motoneurons During Trans-Spinal Direct Current Stimulation.</a> J. Vis. Exp. (2020).
This video describes the in vivo intracellular recording of rat motoneurons under trans-spinal direct current stimulation. The protocol describes how to measure membrane properties and record the rhythmic firing of motoneurons before, during, and after anodal or cathodal polarization of the spinal cord.

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

JoVE Encyclopedia of Experiments

Neurophysiology

Stimulation and Modulation Techniques

Analyzing Neural Activity in Primary Murine Spiral Ganglion Neurons Using Multielectrode Arrays

Source: Hahnewald, S., et al. <a href="https://app.jove.com/v/54538">Spiral Ganglion Neuron Explant Culture and Electrophysiology on Multi Electrode Arrays.</a> J. Vis. Exp. (2016).
This video demonstrates the recording of spontaneous and stimulation-dependent neural activity from primary murine spiral ganglion neuron (SGN) cultures on a multielectrode array (MEA). It involves washing and preparing the MEA, recording spontaneous neural activity, and applying controlled electrical stimuli to identify stimulation-dependent neuronal activity.

All procedures involving animal samples have been reviewed and approved by the appropriate animal ethical review committee.
1. Electrophysiological ...

Electrophysiology Techniques

Microelectrode Array-Based Assessment of Neuronal Networks in Mouse Spinal Cord Slices

Source: Iredale, J. A., et al. <a href="https://app.jove.com/v/62920">Recording Network Activity in Spinal Nociceptive Circuits Using Microelectrode Arrays.</a> J. Vis. Exp. (2022).
This video demonstrates a microelectrode array-based assay for studying neuronal network activity in mouse spinal cord sections. First, the electrophysiological activity from the superficial dorsal horn (SDH) of the slice is recorded. Then, a potassium channel inhibitor is introduced to prolong depolarization, resulting in synchronous rhythmic activity across the neuronal network.

All procedures involving sample collection have been performed in accordance with the institute&#39;s IRB guidelines.
1.&#160;In vitro electrophysiology

	...

In Vivo Single-Fiber Recording of Sciatic Nerve C-Fibers in Rats

Source: Mao, H., et al. <a href="https://app.jove.com/v/59234">Use of In Vivo Single-fiber Recording and Intact Dorsal Root Ganglion with Attached Sciatic Nerve to Examine the Mechanism of Conduction Failure.</a> J. Vis. Exp. (2019).
This video demonstrates a single-fiber recording of C-fiber nerve conduction in rats. An anesthetized rat is incised to expose the sciatic nerve, which provides sensory and motor supply to the lower limbs. The individual C-fibers are then exposed. Electrical stimulation is provided using stimulus electrodes implanted in the foot, and a response is recorded from a single nerve fiber.

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

Measuring the Electrophysiological Activity of Neuronal Networks Using Micro-Electrode Arrays

Acquire the data at 1,200 times amplification and sample the signal at 10 kilohertz using the MCS data acquisition card. Record 20 minutes of electrophysiological activity of hiPSC-derived neurons cultured on MEAs. During the recording, maintain the temperature at 37 degrees Celcius and prevent medium evaporation and pH changes by delivering a constant slow flow of humidified gas onto the MEAs. After that, analyze the data using a custom software package.

Recording Network Activity in Spinal Nociceptive Circuits Using Microelectrode Arrays

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