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Taylor SR, Kobayashi M, Vilella A, Tiwari D, Zolboot N, Du JX, Spencer KR, Hartzell A, Girgiss C, Abaci YT, Shao Y, De Sanctis C, Bellenchi GC, Darnell RB, Gross C, Zoli M, Berg DK, Lippi G. MicroRNA-218 instructs proper assembly of hippocampal networks. eLife 2023; 12:e82729. [PMID: 37862092 PMCID: PMC10637775 DOI: 10.7554/elife.82729] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Accepted: 10/10/2023] [Indexed: 10/21/2023] Open
Abstract
The assembly of the mammalian brain is orchestrated by temporally coordinated waves of gene expression. Post-transcriptional regulation by microRNAs (miRNAs) is a key aspect of this program. Indeed, deletion of neuron-enriched miRNAs induces strong developmental phenotypes, and miRNA levels are altered in patients with neurodevelopmental disorders. However, the mechanisms used by miRNAs to instruct brain development remain largely unexplored. Here, we identified miR-218 as a critical regulator of hippocampal assembly. MiR-218 is highly expressed in the hippocampus and enriched in both excitatory principal neurons (PNs) and GABAergic inhibitory interneurons (INs). Early life inhibition of miR-218 results in an adult brain with a predisposition to seizures. Changes in gene expression in the absence of miR-218 suggest that network assembly is impaired. Indeed, we find that miR-218 inhibition results in the disruption of early depolarizing GABAergic signaling, structural defects in dendritic spines, and altered intrinsic membrane excitability. Conditional knockout of Mir218-2 in INs, but not PNs, is sufficient to recapitulate long-term instability. Finally, de-repressing Kif21b and Syt13, two miR-218 targets, phenocopies the effects on early synchronous network activity induced by miR-218 inhibition. Taken together, the data suggest that miR-218 orchestrates formative events in PNs and INs to produce stable networks.
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Affiliation(s)
- Seth R Taylor
- Division of Biological Sciences, University of California, San DiegoLa JollaUnited States
| | - Mariko Kobayashi
- Laboratory of Molecular Neuro-oncology, Howard Hughes Medical Institute, Rockefeller UniversityNew YorkUnited States
| | - Antonietta Vilella
- Department of Biomedical, Metabolic and Neural Sciences; Center for Neuroscience and Neurotechnology (CfNN), University of Modena and Reggio EmiliaModenaItaly
| | - Durgesh Tiwari
- Division of Neurology, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati College of MedicineCincinnatiUnited States
- Department of Pediatrics, University of Cincinnati College of MedicineCincinnatiUnited States
| | - Norjin Zolboot
- Department of Neuroscience, Scripps Research InstituteLa JollaUnited States
| | - Jessica X Du
- Department of Neuroscience, Scripps Research InstituteLa JollaUnited States
| | - Kathryn R Spencer
- Department of Neuroscience, Scripps Research InstituteLa JollaUnited States
| | - Andrea Hartzell
- Department of Neuroscience, Scripps Research InstituteLa JollaUnited States
| | - Carol Girgiss
- Division of Biological Sciences, University of California, San DiegoLa JollaUnited States
| | - Yusuf T Abaci
- Division of Biological Sciences, University of California, San DiegoLa JollaUnited States
| | - Yufeng Shao
- Department of Neuroscience, Scripps Research InstituteLa JollaUnited States
| | | | - Gian Carlo Bellenchi
- Institute of Genetics and Biophysics A Buzzati-TraversoNaplesItaly
- IRCCS Fondazione Santa LuciaRomeItaly
| | - Robert B Darnell
- Laboratory of Molecular Neuro-oncology, Howard Hughes Medical Institute, Rockefeller UniversityNew YorkUnited States
| | - Christina Gross
- Division of Neurology, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati College of MedicineCincinnatiUnited States
- Department of Pediatrics, University of Cincinnati College of MedicineCincinnatiUnited States
| | - Michele Zoli
- Department of Biomedical, Metabolic and Neural Sciences; Center for Neuroscience and Neurotechnology (CfNN), University of Modena and Reggio EmiliaModenaItaly
| | - Darwin K Berg
- Division of Biological Sciences, University of California, San DiegoLa JollaUnited States
| | - Giordano Lippi
- Department of Neuroscience, Scripps Research InstituteLa JollaUnited States
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2
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Hoynoski J, Dohn J, Franzen AD, Burrell BD. Repetitive nociceptive stimulation elicits complex behavioral changes in Hirudo: evidence of arousal and motivational adaptations. J Exp Biol 2023; 226:jeb245895. [PMID: 37497630 PMCID: PMC10445732 DOI: 10.1242/jeb.245895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Accepted: 07/20/2023] [Indexed: 07/28/2023]
Abstract
Appropriate responses to real or potential damaging stimuli to the body (nociception) are critical to an animal's short- and long-term survival. The initial goal of this study was to examine habituation of withdrawal reflexes (whole-body and local shortening) to repeated mechanical nociceptive stimuli (needle pokes) in the medicinal leech, Hirudo verbana, and assess whether injury altered habituation to these nociceptive stimuli. While repeated needle pokes did reduce shortening in H. verbana, a second set of behavior changes was observed. Specifically, animals began to evade subsequent stimuli by either hiding their posterior sucker underneath adjacent body segments or engaging in locomotion (crawling). Animals differed in terms of how quickly they adopted evasion behaviors during repeated stimulation, exhibiting a multi-modal distribution for early, intermediate and late evaders. Prior injury had a profound effect on this transition, decreasing the time frame in which animals began to carry out evasion and increasing the magnitude of these evasion behaviors (more locomotory evasion). The data indicate the presence in Hirudo of a complex and adaptive defensive arousal process to avoid noxious stimuli that is influenced by differences in internal states, prior experience with injury of the stimulated areas, and possibly learning-based processes.
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Affiliation(s)
- Jessica Hoynoski
- Division of Basic Biomedical Sciences, Center for Brain and Behavioral Research (CBBRe), Sanford School of Medicine, University of South Dakota, Vermillion, SD 57069, USA
| | - John Dohn
- Division of Basic Biomedical Sciences, Center for Brain and Behavioral Research (CBBRe), Sanford School of Medicine, University of South Dakota, Vermillion, SD 57069, USA
| | - Avery D. Franzen
- Division of Basic Biomedical Sciences, Center for Brain and Behavioral Research (CBBRe), Sanford School of Medicine, University of South Dakota, Vermillion, SD 57069, USA
| | - Brian D. Burrell
- Division of Basic Biomedical Sciences, Center for Brain and Behavioral Research (CBBRe), Sanford School of Medicine, University of South Dakota, Vermillion, SD 57069, USA
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3
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Meiser S, Sleeboom JM, Arkhypchuk I, Sandbote K, Kretzberg J. Cell anatomy and network input explain differences within but not between leech touch cells at two different locations. Front Cell Neurosci 2023; 17:1186997. [PMID: 37565030 PMCID: PMC10411907 DOI: 10.3389/fncel.2023.1186997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Accepted: 07/06/2023] [Indexed: 08/12/2023] Open
Abstract
Mechanosensory cells in the leech share several common features with mechanoreceptors in the human glabrous skin. Previous studies showed that the six T (touch) cells in each body segment of the leech are highly variable in their responses to somatic current injection and change their excitability over time. Here, we investigate three potential reasons for this variability in excitability by comparing the responses of T cells at two soma locations (T2 and T3): (1) Differential effects of time-dependent changes in excitability, (2) divergent synaptic input from the network, and (3) different anatomical structures. These hypotheses were explored with a combination of electrophysiological double recordings, 3D reconstruction of neurobiotin-filled cells, and compartmental model simulations. Current injection triggered significantly more spikes with shorter latency and larger amplitudes in cells at soma location T2 than at T3. During longer recordings, cells at both locations increased their excitability over time in the same way. T2 and T3 cells received the same amount of synaptic input from the unstimulated network, and the polysynaptic connections between both T cells were mutually symmetric. However, we found a striking anatomical difference: While in our data set all T2 cells innervated two roots connecting the ganglion with the skin, 50% of the T3 cells had only one root process. The sub-sample of T3 cells with one root process was significantly less excitable than the T3 cells with two root processes and the T2 cells. To test if the additional root process causes higher excitability, we simulated the responses of 3D reconstructed cells of both anatomies with detailed multi-compartment models. The anatomical subtypes do not differ in excitability when identical biophysical parameters and a homogeneous channel distribution are assumed. Hence, all three hypotheses may contribute to the highly variable T cell responses, but none of them is the only factor accounting for the observed systematic difference in excitability between cells at T2 vs. T3 soma location. Therefore, future patch clamp and modeling studies are needed to analyze how biophysical properties and spatial distribution of ion channels on the cell surface contribute to the variability and systematic differences of electrophysiological phenotypes.
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Affiliation(s)
- Sonja Meiser
- Department of Neuroscience, Computational Neuroscience, Faculty VI, University of Oldenburg, Oldenburg, Germany
| | - Jana Marie Sleeboom
- Department of Neuroscience, Computational Neuroscience, Faculty VI, University of Oldenburg, Oldenburg, Germany
- Institute of Physiology II, Faculty of Medicine, University Clinic Bonn (UKB), University of Bonn, Bonn, Germany
| | - Ihor Arkhypchuk
- Department of Neuroscience, Computational Neuroscience, Faculty VI, University of Oldenburg, Oldenburg, Germany
| | - Kevin Sandbote
- Department of Neuroscience, Computational Neuroscience, Faculty VI, University of Oldenburg, Oldenburg, Germany
| | - Jutta Kretzberg
- Department of Neuroscience, Computational Neuroscience, Faculty VI, University of Oldenburg, Oldenburg, Germany
- Department of Neuroscience, Cluster of Excellence Hearing4all, Faculty VI, University of Oldenburg, Oldenburg, Germany
- Research Center Neurosensory Science, University of Oldenburg, Oldenburg, Germany
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4
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Walker AS, Raliski BK, Karbasi K, Zhang P, Sanders K, Miller EW. Optical Spike Detection and Connectivity Analysis With a Far-Red Voltage-Sensitive Fluorophore Reveals Changes to Network Connectivity in Development and Disease. Front Neurosci 2021; 15:643859. [PMID: 34054405 PMCID: PMC8155641 DOI: 10.3389/fnins.2021.643859] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Accepted: 03/10/2021] [Indexed: 12/14/2022] Open
Abstract
The ability to optically record dynamics of neuronal membrane potential promises to revolutionize our understanding of neurobiology. In this study, we show that the far-red voltage sensitive fluorophore, Berkeley Red Sensor of Transmembrane potential-1, or BeRST 1, can be used to monitor neuronal membrane potential changes across dozens of neurons at a sampling rate of 500 Hz. Notably, voltage imaging with BeRST 1 can be implemented with affordable, commercially available illumination sources, optics, and detectors. BeRST 1 is well-tolerated in cultures of rat hippocampal neurons and provides exceptional optical recording fidelity, as judged by dual fluorescence imaging and patch-clamp electrophysiology. We developed a semi-automated spike-picking program to reduce user bias when calling action potentials and used this in conjunction with BeRST 1 to develop an optical spike and connectivity analysis (OSCA) for high-throughput dissection of neuronal activity dynamics. The high temporal resolution of BeRST 1 enables dissection of firing rate changes in response to acute, pharmacological interventions with commonly used inhibitors like gabazine and picrotoxin. Over longer periods of time, BeRST 1 also tracks chronic perturbations to neurons exposed to amyloid beta 1-42 (Aβ 1-42), revealing modest changes to spiking frequency but profound changes to overall network connectivity. Finally, we use OSCA to track changes in neuronal connectivity during maturation in culture, providing a functional readout of network assembly. We envision that use of BeRST 1 and OSCA described here will be of use to the broad neuroscience community.
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Affiliation(s)
- Alison S. Walker
- Department of Chemistry, University of California, Berkeley, Berkeley, CA, United States
- Department of Molecular & Cell Biology, University of California, Berkeley, Berkeley, CA, United States
- Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA, United States
| | - Benjamin K. Raliski
- Department of Chemistry, University of California, Berkeley, Berkeley, CA, United States
| | - Kaveh Karbasi
- Department of Chemistry, University of California, Berkeley, Berkeley, CA, United States
| | - Patrick Zhang
- Department of Chemistry, University of California, Berkeley, Berkeley, CA, United States
| | - Kate Sanders
- Department of Chemistry, University of California, Berkeley, Berkeley, CA, United States
| | - Evan W. Miller
- Department of Chemistry, University of California, Berkeley, Berkeley, CA, United States
- Department of Molecular & Cell Biology, University of California, Berkeley, Berkeley, CA, United States
- Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA, United States
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5
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Abstract
Membrane potential is a fundamental biophysical property maintained by every cell on earth. In specialized cells like neurons, rapid changes in membrane potential drive the release of chemical neurotransmitters. Coordinated, rapid changes in neuronal membrane potential across large numbers of interconnected neurons form the basis for all of human cognition, sensory perception, and memory. Despite the importance of this highly orchestrated and distributed activity, the traditional method for recording membrane potential is through the use of highly invasive single-cell electrodes that offer only a small glimpse of the total activity within a system. Fluorescent dyes that change their optical properties in response to changes in biological voltage have the potential to provide a powerful complement to traditional electrode-based methods of inquiry. Voltage-sensitive fluorescent indicators would allow the direct observation of membrane potential changes, significantly expanding our ability to monitor membrane potential dynamics in living systems. Toward this end, we have initiated a program to design, synthesize, and apply voltage-sensitive fluorophores that report on membrane potential dynamics with high sensitivity and speed. The basis for this optical voltage sensing is membrane potential-dependent photoinduced electron transfer (PeT). Voltage-sensitive fluorophores, or VoltageFluors, possess a fluorophore, a conjugated molecular wire, and an aniline donor. At resting potentials, in which the cell has a hyperpolarized or negative potential relative to the outside of the cell, PeT from the aniline donor is enhanced and fluorescence is diminished. At depolarized potentials, the membrane potential decreases the rate of PeT, allowing an increase in fluorescence. We show that a number of different fluorophores, molecular wires, and aniline donors can be employed to generate fast and sensitive VoltageFluor dyes. Multiple lines of evidence point to a PeT-based mechanism for voltage sensing, delivering fast response kinetics (∼25 ns), good sensitivity (>60% ΔF/F), compatibility with two-photon illumination, excellent signal-to-noise, and the ability to detect neuronal and cardiac action potentials in single trials. In this Account, we provide an overview of the challenges facing the design of fluorescent voltage indicators. We trace the development of molecular wire-based fluorescent voltage indicators within our group, beginning from fluorescein-based VoltageFluor to long-wavelength indicators that use modern fluorophores like silicon rhodamine and carbofluorescein. We examine design principles for PeT-based voltage indicators, showcase the use of our recent indicators for two-photon voltage imaging in intact brains, and explore the development of hybrid indicators that can localize to genetically defined cells. Finally, we highlight outstanding challenges to and opportunities for voltage imaging.
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Affiliation(s)
- Pei Liu
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Evan W. Miller
- Department of Chemistry, University of California, Berkeley, California 94720, United States
- Department of Molecular & Cell Biology, University of California, Berkeley, California 94720, United States
- Department of Helen Wills Neuroscience Institute. University of California, Berkeley, California 94720, United States
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6
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Meiser S, Ashida G, Kretzberg J. Non-synaptic Plasticity in Leech Touch Cells. Front Physiol 2019; 10:1444. [PMID: 31827443 PMCID: PMC6890822 DOI: 10.3389/fphys.2019.01444] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Accepted: 11/08/2019] [Indexed: 01/06/2023] Open
Abstract
The role of Na+/K+-pumps in activity-dependent synaptic plasticity has been described in both vertebrates and invertebrates. Here, we provide evidence that the Na+/K+-pump is also involved in activity-dependent non-synaptic cellular plasticity in leech sensory neurons. We show that the resting membrane potential (RMP) of T cells hyperpolarizes in response to repeated somatic current injection, while at the same time their spike count (SC) and the input resistance (IR) increase. Our Hodgkin–Huxley-type neuron model, adjusted to physiological T cell properties, suggests that repetitive action potential discharges lead to increased Na+/K+-pump activity, which then hyperpolarizes the RMP. In consequence, a slow, non-inactivating current decreases, which is presumably mediated by voltage-dependent, low-threshold potassium channels. Closing of these putative M-type channels due to hyperpolarization of the resting potential increases the IR of the cell, leading to a larger number of spikes. By this mechanism, the response behavior switches from rapidly to slowly adapting spiking. These changes in spiking behavior also effect other T cells on the same side of the ganglion, which are connected via a combination of electrical and chemical synapses. An increased SC in the presynaptic T cell results in larger postsynaptic responses (PRs) in the other T cells. However, when the number of elicited presynaptic spikes is kept constant, the PR does not change. These results suggest that T cells change their responses in an activity-dependent manner through non-synaptic rather than synaptic plasticity. These changes might act as a gain-control mechanism. Depending on the previous activity, this gain could scale the relative impacts of synaptic inputs from other mechanoreceptors, versus the spike responses to tactile skin stimulation. This multi-tasking ability, and its flexible adaptation to previous activity, might make the T cell a key player in a preparatory network, enabling the leech to perform fast behavioral reactions to skin stimulation.
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Affiliation(s)
- Sonja Meiser
- Computational Neuroscience, Department of Neuroscience, Faculty VI, Carl von Ossietzky University of Oldenburg, Oldenburg, Germany
| | - Go Ashida
- Computational Neuroscience, Department of Neuroscience, Faculty VI, Carl von Ossietzky University of Oldenburg, Oldenburg, Germany.,Cluster of Excellence Hearing4all, Department of Neuroscience, Faculty VI, Carl von Ossietzky University of Oldenburg, Oldenburg, Germany
| | - Jutta Kretzberg
- Computational Neuroscience, Department of Neuroscience, Faculty VI, Carl von Ossietzky University of Oldenburg, Oldenburg, Germany.,Cluster of Excellence Hearing4all, Department of Neuroscience, Faculty VI, Carl von Ossietzky University of Oldenburg, Oldenburg, Germany
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7
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Fathiazar E, Hilgen G, Kretzberg J. Higher Network Activity Induced by Tactile Compared to Electrical Stimulation of Leech Mechanoreceptors. Front Physiol 2018; 9:173. [PMID: 29563881 PMCID: PMC5845893 DOI: 10.3389/fphys.2018.00173] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Accepted: 02/20/2018] [Indexed: 11/29/2022] Open
Abstract
The tiny ensemble of neurons in the leech ganglion can discriminate the locations of touch stimuli on the skin as precisely as a human fingertip. The leech uses this ability to locally bend the body-wall away from the stimulus. It is assumed that a three-layered feedforward network of pressure mechanoreceptors, interneurons, and motor neurons controls this behavior. Most previous studies identified and characterized the local bend network based on electrical stimulation of a single pressure mechanoreceptor, which was sufficient to trigger the local bend response. Recent studies showed, however, that up to six mechanoreceptors of three types innervating the stimulated patch of skin carry information about both touch intensity and location simultaneously. Therefore, we hypothesized that interneurons involved in the local bend network might require the temporally concerted inputs from the population of mechanoreceptors representing tactile stimuli, to decode the tactile information and to provide appropriate synaptic inputs to the motor neurons. We examined the influence of current injection into a single mechanoreceptor on activity of postsynaptic interneurons in the network and compared it to responses of interneurons to skin stimulation with different pressure intensities. We used voltage-sensitive dye imaging to monitor the graded membrane potential changes of all visible cells on the ventral side of the ganglion. Our results showed that stimulation of a single mechanoreceptor activates several local bend interneurons, consistent with previous intracellular studies. Tactile skin stimulation, however, evoked a more pronounced, longer-lasting, stimulus intensity-dependent network dynamics involving more interneurons. We concluded that the underlying local bend network enables a non-linear processing of tactile information provided by population of mechanoreceptors. This task requires a more complex network structure than previously assumed, probably containing polysynaptic interneuron connections and feedback loops. This small, experimentally well-accessible neuronal system highlights the general importance of selecting adequate sensory stimulation to investigate the network dynamics in the context of natural behavior.
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Affiliation(s)
- Elham Fathiazar
- Computational Neuroscience, Department of Neuroscience, FK VI, University of Oldenburg, Oldenburg, Germany
| | - Gerrit Hilgen
- Computational Neuroscience, Department of Neuroscience, FK VI, University of Oldenburg, Oldenburg, Germany.,Faculty of Medical Sciences, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Jutta Kretzberg
- Computational Neuroscience, Department of Neuroscience, FK VI, University of Oldenburg, Oldenburg, Germany.,Cluster of Excellence Hearing4all, University of Oldenburg, Oldenburg, Germany
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8
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Pirschel F, Hilgen G, Kretzberg J. Effects of Touch Location and Intensity on Interneurons of the Leech Local Bend Network. Sci Rep 2018; 8:3046. [PMID: 29445203 PMCID: PMC5813025 DOI: 10.1038/s41598-018-21272-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Accepted: 01/24/2018] [Indexed: 11/09/2022] Open
Abstract
Touch triggers highly precise behavioural responses in the leech. The underlying network of this so-called local bend reflex consists of three layers of individually characterised neurons. While the population of mechanosensory cells provide multiplexed information about the stimulus, not much is known about how interneurons process this information. Here, we analyse the responses of two local bend interneurons (cell 157 and 159) to a mechanical stimulation of the skin and show their response characteristics to naturalistic stimuli. Intracellular dye-fills combined with structural imaging revealed that these interneurons are synaptically coupled to all three types of mechanosensory cells (T, P, and N cells). Since tactile stimulation of the skin evokes spikes in one to two cells of each of the latter types, interneurons combine inputs from up to six mechanosensory cells. We find that properties of touch location and intensity can be estimated reliably and accurately based on the graded interneuron responses. Connections to several mechanosensory cell types and specific response characteristics of the interneuron types indicate specialised filter and integration properties within this small neuronal network, thus providing evidence for more complex signal processing than previously thought.
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Affiliation(s)
- Friederice Pirschel
- Computational Neuroscience, Department for Neuroscience, University of Oldenburg, Oldenburg, Germany. .,Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL, USA.
| | - Gerrit Hilgen
- Computational Neuroscience, Department for Neuroscience, University of Oldenburg, Oldenburg, Germany.,Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Jutta Kretzberg
- Computational Neuroscience, Department for Neuroscience, University of Oldenburg, Oldenburg, Germany.,Cluster of Excellence "Hearing4all", University of Oldenburg, Oldenburg, Germany
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9
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Abstract
In this protocol, we introduce an effective method for voltage-sensitive dye (VSD) loading and imaging of leech ganglia as used in Tomina and Wagenaar (2017). Dissection and dye loading procedures are the most critical steps toward successful whole-ganglion VSD imaging. The former entails the removal of the sheath that covers neurons in the segmental ganglion of the leech, which is required for successful dye loading. The latter entails gently flowing a new generation VSD, VF2.1(OMe).H, onto both sides of the ganglion simultaneously using a pair of peristaltic pumps. We expect the described techniques to translate broadly to wide-field VSD imaging in other thin and relatively transparent nervous systems.
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Affiliation(s)
- Yusuke Tomina
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, United States
| | - Daniel A Wagenaar
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, United States
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10
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Humphries MD. Dynamical networks: Finding, measuring, and tracking neural population activity using network science. Netw Neurosci 2017; 1:324-338. [PMID: 30090869 PMCID: PMC6063717 DOI: 10.1162/netn_a_00020] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Accepted: 06/06/2017] [Indexed: 11/04/2022] Open
Abstract
Systems neuroscience is in a headlong rush to record from as many neurons at the same time as possible. As the brain computes and codes using neuron populations, it is hoped these data will uncover the fundamentals of neural computation. But with hundreds, thousands, or more simultaneously recorded neurons come the inescapable problems of visualizing, describing, and quantifying their interactions. Here I argue that network science provides a set of scalable, analytical tools that already solve these problems. By treating neurons as nodes and their interactions as links, a single network can visualize and describe an arbitrarily large recording. I show that with this description we can quantify the effects of manipulating a neural circuit, track changes in population dynamics over time, and quantitatively define theoretical concepts of neural populations such as cell assemblies. Using network science as a core part of analyzing population recordings will thus provide both qualitative and quantitative advances to our understanding of neural computation.
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Affiliation(s)
- Mark D. Humphries
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
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11
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Tomina Y, Wagenaar DA. A double-sided microscope to realize whole-ganglion imaging of membrane potential in the medicinal leech. eLife 2017; 6:29839. [PMID: 28944754 PMCID: PMC5656430 DOI: 10.7554/elife.29839] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Accepted: 09/25/2017] [Indexed: 12/15/2022] Open
Abstract
Studies of neuronal network emergence during sensory processing and motor control are greatly facilitated by technologies that allow us to simultaneously record the membrane potential dynamics of a large population of neurons in single cell resolution. To achieve whole-brain recording with the ability to detect both small synaptic potentials and action potentials, we developed a voltage-sensitive dye (VSD) imaging technique based on a double-sided microscope that can image two sides of a nervous system simultaneously. We applied this system to the segmental ganglia of the medicinal leech. Double-sided VSD imaging enabled simultaneous recording of membrane potential events from almost all of the identifiable neurons. Using data obtained from double-sided VSD imaging, we analyzed neuronal dynamics in both sensory processing and generation of behavior and constructed functional maps for identification of neurons contributing to these processes. In every animal, networks of nerve cells work together to interpret signals from the environment and to coordinate responses. Being able to record the activity of all the neurons in a brain at once would greatly advance our understanding of how the brain works. Yet it is not possible to do this for a human brain, which contains several billion neurons. The medicinal leech, on the other hand, has a much simpler nervous system. It has 21 brain-like units called segmental ganglia, which control how the parts of its body move, and each one contains about 400 neurons arranged on a single layer. The activity of large populations of neurons can be monitored using a technique called fluorescent imaging. Most fluorescent dyes, however, are not sensitive enough to report low levels of activity or fast enough to track individual nerve impulses. Also, current microscopy techniques only allow one surface to be imaged at any one time. These limitations constrain the kinds of questions that neuroscientists can ask about how networks of nerve cells function. Tomina and Wagenaar have now developed a double-sided fluorescent microscope system that allows a ganglion in a medicinal leech to be viewed from both sides at once. Using a new generation of dyes, which rapidly change their brightness as individual neurons become active or are inhibited, subtle changes in the activity of hundreds of individual neurons were monitored at the same time. In a test of the system, Tomina and Wagenaar recorded activity for different leech behaviors, like bending, swimming and crawling. For the first time, the relationships between neurons on both sides of the ganglion could be seen. This new technique for examining the activity in neuronal circuitry will allow complex networks of neurons to be studied in more detail. The data that these images generate could then be analyzed mathematically to better understand how the brain processes information from its senses and generates behavior.
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Affiliation(s)
- Yusuke Tomina
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, United States
| | - Daniel A Wagenaar
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, United States
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12
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Neveu CL, Costa RM, Homma R, Nagayama S, Baxter DA, Byrne JH. Unique Configurations of Compression and Truncation of Neuronal Activity Underlie l-DOPA-Induced Selection of Motor Patterns in Aplysia. eNeuro 2017; 4:ENEURO.0206-17.2017. [PMID: 29071298 PMCID: PMC5654236 DOI: 10.1523/eneuro.0206-17.2017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Revised: 09/05/2017] [Accepted: 09/28/2017] [Indexed: 12/29/2022] Open
Abstract
A key issue in neuroscience is understanding the ways in which neuromodulators such as dopamine modify neuronal activity to mediate selection of distinct motor patterns. We addressed this issue by applying either low or high concentrations of l-DOPA (40 or 250 μM) and then monitoring activity of up to 130 neurons simultaneously in the feeding circuitry of Aplysia using a voltage-sensitive dye (RH-155). l-DOPA selected one of two distinct buccal motor patterns (BMPs): intermediate (low l-DOPA) or bite (high l-DOPA) patterns. The selection of intermediate BMPs was associated with shortening of the second phase of the BMP (retraction), whereas the selection of bite BMPs was associated with shortening of both phases of the BMP (protraction and retraction). Selection of intermediate BMPs was also associated with truncation of individual neuron spike activity (decreased burst duration but no change in spike frequency or burst latency) in neurons active during retraction. In contrast, selection of bite BMPs was associated with compression of spike activity (decreased burst latency and duration and increased spike frequency) in neurons projecting through specific nerves, as well as increased spike frequency of protraction neurons. Finally, large-scale voltage-sensitive dye recordings delineated the spatial distribution of neurons active during BMPs and the modification of that distribution by the two concentrations of l-DOPA.
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Affiliation(s)
- Curtis L Neveu
- Department of Neurobiology and Anatomy, W. M. Keck Center for the Neurobiology of Learning and Memory, McGovern Medical School at the University of Texas Health Science Center at Houston, Houston, TX 77030
| | - Renan M Costa
- Department of Neurobiology and Anatomy, W. M. Keck Center for the Neurobiology of Learning and Memory, McGovern Medical School at the University of Texas Health Science Center at Houston, Houston, TX 77030
| | - Ryota Homma
- Department of Neurobiology and Anatomy, W. M. Keck Center for the Neurobiology of Learning and Memory, McGovern Medical School at the University of Texas Health Science Center at Houston, Houston, TX 77030
| | - Shin Nagayama
- Department of Neurobiology and Anatomy, W. M. Keck Center for the Neurobiology of Learning and Memory, McGovern Medical School at the University of Texas Health Science Center at Houston, Houston, TX 77030
| | - Douglas A Baxter
- Department of Neurobiology and Anatomy, W. M. Keck Center for the Neurobiology of Learning and Memory, McGovern Medical School at the University of Texas Health Science Center at Houston, Houston, TX 77030
| | - John H Byrne
- Department of Neurobiology and Anatomy, W. M. Keck Center for the Neurobiology of Learning and Memory, McGovern Medical School at the University of Texas Health Science Center at Houston, Houston, TX 77030
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Kulkarni RU, Yin H, Pourmandi N, James F, Adil MM, Schaffer DV, Wang Y, Miller EW. A Rationally Designed, General Strategy for Membrane Orientation of Photoinduced Electron Transfer-Based Voltage-Sensitive Dyes. ACS Chem Biol 2017; 12:407-413. [PMID: 28004909 DOI: 10.1021/acschembio.6b00981] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Voltage imaging with fluorescent dyes offers promise for interrogating the complex roles of membrane potential in coordinating the activity of neurons in the brain. Yet, low sensitivity often limits the broad applicability of optical voltage indicators. In this paper, we use molecular dynamics (MD) simulations to guide the design of new, ultrasensitive fluorescent voltage indicators that use photoinduced electron transfer (PeT) as a voltage-sensing switch. MD simulations predict an approximately 16% increase in voltage sensitivity resulting purely from improved alignment of dye with the membrane. We confirm this theoretical finding by synthesizing 9 new voltage-sensitive (VoltageFluor, or VF) dyes and establishing that all of them display the expected improvement of approximately 19%. This synergistic outworking of theory and experiment enabled computational and theoretical estimation of VF dye orientation in lipid bilayers and has yielded the most sensitive PeT-based VF dye to date. We use this new voltage indicator to monitor voltage spikes in neurons from rat hippocampus and human pluripotent-stem-cell-derived dopaminergic neurons.
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Affiliation(s)
| | - Hang Yin
- Shenzhen
Research Institute and Department of Physics, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong
| | | | | | | | | | - Yi Wang
- Shenzhen
Research Institute and Department of Physics, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong
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