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Cook AP, Nusbaum MP. Feeding state-dependent modulation of feeding-related motor patterns. J Neurophysiol 2021; 126:1903-1924. [PMID: 34669505 PMCID: PMC8715047 DOI: 10.1152/jn.00387.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 10/12/2021] [Accepted: 10/13/2021] [Indexed: 11/22/2022] Open
Abstract
Studies elucidating modulation of microcircuit activity in isolated nervous systems have revealed numerous insights regarding neural circuit flexibility, but this approach limits the link between experimental results and behavioral context. To bridge this gap, we studied feeding behavior-linked modulation of microcircuit activity in the isolated stomatogastric nervous system (STNS) of male Cancer borealis crabs. Specifically, we removed hemolymph from a crab that was unfed for ≥24 h ("unfed" hemolymph) or fed 15 min to 2 h before hemolymph removal ("fed" hemolymph). After feeding, the first significant foregut emptying occurred >1 h later and complete emptying required ≥6 h. We applied the unfed or fed hemolymph to the stomatogastric ganglion (STG) in an isolated STNS preparation from a separate, unfed crab to determine its influence on the VCN (ventral cardiac neuron)-triggered gastric mill (chewing) and pyloric (filtering of chewed food) rhythms. Unfed hemolymph had little influence on these rhythms, but fed hemolymph from each examined time-point (15 min, 1 h, or 2 h after feeding) slowed one or both rhythms without weakening circuit neuron activity. There were also distinct parameter changes associated with each time-point. One change unique to the 1-h time-point (i.e., reduced activity of one circuit neuron during the transition from the gastric mill retraction to protraction phase) suggested that the fed hemolymph also enhanced the influence of a projection neuron that innervates the STG from a ganglion isolated from the applied hemolymph. Hemolymph thus provides a feeding state-dependent modulation of the two feeding-related motor patterns in the C. borealis STG.NEW & NOTEWORTHY Little is known about behavior-linked modulation of microcircuit activity. We show that the VCN-triggered gastric mill (chewing) and pyloric (food filtering) rhythms in the isolated crab Cancer borealis stomatogastric nervous system were changed by applying hemolymph from recently fed but not unfed crabs. This included some distinct parameter changes during each examined post-fed hemolymph time-point. These results suggest the presence of feeding-related changes in circulating hormones that regulate consummatory microcircuit activity.
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Affiliation(s)
- Aaron P Cook
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Michael P Nusbaum
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
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Synaptic Dynamics Convey Differential Sensitivity to Input Pattern Changes in Two Muscles Innervated by the Same Motor Neurons. eNeuro 2021; 8:ENEURO.0351-21.2021. [PMID: 34764189 PMCID: PMC8609967 DOI: 10.1523/eneuro.0351-21.2021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 09/21/2021] [Accepted: 09/30/2021] [Indexed: 11/21/2022] Open
Abstract
Postsynaptic responses depend on input patterns as well as short-term synaptic plasticity, summation, and postsynaptic membrane properties, but the interactions of those dynamics with realistic input patterns are not well understood. We recorded the responses of the two pyloric dilator (PD) muscles, cpv2a and cpv2b, that are innervated by and receive identical periodic bursting input from the same two motor neurons in the lobster Homarus americanus. Cpv2a and cpv2b showed quantitative differences in membrane nonlinearities and synaptic summation. At a short timescale, responses in both muscles were dominated by facilitation, albeit with different frequency and time dependence. Realistic burst stimulations revealed more substantial differences. Across bursts, cpv2a showed transient depression, whereas cpv2b showed transient facilitation. Steady-state responses to bursting input also differed substantially. Neither muscle had a monotonic dependence on frequency, but cpv2b showed particularly pronounced bandpass filtering. Cpv2a was sensitive to changes in both burst frequency and intra-burst spike frequency, whereas, despite its much slower responses, cpv2b was largely insensitive to changes in burst frequency. Cpv2a was sensitive to both burst duration and number of spikes per burst, whereas cpv2b was sensitive only to the former parameter. Neither muscle showed consistent sensitivity to changes in the overall spike interval structure, but cpv2b was surprisingly sensitive to changes in the first intervals in each burst, a parameter known to be regulated by dopamine (DA) modulation of spike propagation of the presynaptic axon. These findings highlight how seemingly minor circuit output changes mediated by neuromodulation could be read out differentially at the two synapses.
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Powell DJ, Marder E, Nusbaum MP. Perturbation-specific responses by two neural circuits generating similar activity patterns. Curr Biol 2021; 31:4831-4838.e4. [PMID: 34506730 DOI: 10.1016/j.cub.2021.08.042] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 07/07/2021] [Accepted: 08/13/2021] [Indexed: 01/30/2023]
Abstract
A fundamental question in neuroscience is whether neuronal circuits with variable circuit parameters that produce similar outputs respond comparably to equivalent perturbations.1-4 Work on the pyloric rhythm of the crustacean stomatogastric ganglion (STG) showed that highly variable sets of intrinsic and synaptic conductances can generate similar circuit activity patterns.5-9 Importantly, in response to physiologically relevant perturbations, these disparate circuit solutions can respond robustly and reliably,10-12 but when exposed to extreme perturbations the underlying circuit parameter differences produce diverse patterns of disrupted activity.7,12,13 In this example, the pyloric circuit is unchanged; only the conductance values vary. In contrast, the gastric mill rhythm in the STG can be generated by distinct circuits when activated by different modulatory neurons and/or neuropeptides.14-21 Generally, these distinct circuits produce different gastric mill rhythms. However, the rhythms driven by stimulating modulatory commissural neuron 1 (MCN1) and bath-applying CabPK (Cancer borealis pyrokinin) peptide generate comparable output patterns, despite having distinct circuits that use separate cellular and synaptic mechanisms.22-25 Here, we use these two gastric mill circuits to determine whether such circuits respond comparably when challenged with persisting (hormonal: CCAP) or acute (sensory: GPR neuron) metabotropic influences. Surprisingly, the hormone-mediated action separates these two rhythms despite activating the same ionic current in the same circuit neuron during both rhythms, whereas the sensory neuron evokes comparable responses despite acting via different synapses during each rhythm. These results highlight the need for caution when inferring the circuit response to a perturbation when that circuit is not well defined physiologically.
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Affiliation(s)
- Daniel J Powell
- Volen Center for Complex Systems and Department of Biology, Brandeis University, 415 South Street, Waltham, MA 02454, USA
| | - Eve Marder
- Volen Center for Complex Systems and Department of Biology, Brandeis University, 415 South Street, Waltham, MA 02454, USA
| | - Michael P Nusbaum
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, 211 CRB, 415 Curie Boulevard, Philadelphia, PA 19104, USA.
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Colton GF, Cook AP, Nusbaum MP. Different microcircuit responses to comparable input from one versus both copies of an identified projection neuron. J Exp Biol 2020; 223:jeb228114. [PMID: 32820029 PMCID: PMC7648612 DOI: 10.1242/jeb.228114] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Accepted: 08/13/2020] [Indexed: 12/19/2022]
Abstract
Neuronal inputs to microcircuits are often present as multiple copies of apparently equivalent neurons. Thus far, however, little is known regarding the relative influence on microcircuit output of activating all or only some copies of such an input. We examine this issue in the crab (Cancer borealis) stomatogastric ganglion, where the gastric mill (chewing) microcircuit is activated by modulatory commissural neuron 1 (MCN1), a bilaterally paired modulatory projection neuron. Both MCN1s contain the same co-transmitters, influence the same gastric mill microcircuit neurons, can drive the biphasic gastric mill rhythm, and are co-activated by all identified MCN1-activating pathways. Here, we determine whether the gastric mill microcircuit response is equivalent when stimulating one or both MCN1s under conditions where the pair are matched to collectively fire at the same overall rate and pattern as single MCN1 stimulation. The dual MCN1 stimulations elicited more consistently coordinated rhythms, and these rhythms exhibited longer phases and cycle periods. These different outcomes from single and dual MCN1 stimulation may have resulted from the relatively modest, and equivalent, firing rate of the gastric mill neuron LG (lateral gastric) during each matched set of stimulations. The LG neuron-mediated, ionotropic inhibition of the MCN1 axon terminals is the trigger for the transition from the retraction to protraction phase. This LG neuron influence on MCN1 was more effective during the dual stimulations, where each MCN1 firing rate was half that occurring during the matched single stimulations. Thus, equivalent individual- and co-activation of a class of modulatory projection neurons does not necessarily drive equivalent microcircuit output.
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Affiliation(s)
- Gabriel F Colton
- Department of Neuroscience, 211 Clinical Research Building, 415 Curie Boulevard, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Aaron P Cook
- Department of Neuroscience, 211 Clinical Research Building, 415 Curie Boulevard, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Michael P Nusbaum
- Department of Neuroscience, 211 Clinical Research Building, 415 Curie Boulevard, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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Afolabi BA, Olagoke OC. High concentration of MSG alters antioxidant defence system in lobster cockroach Nauphoeta cinerea (Blattodea: Blaberidae). BMC Res Notes 2020; 13:217. [PMID: 32299491 PMCID: PMC7164354 DOI: 10.1186/s13104-020-05056-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Accepted: 04/01/2020] [Indexed: 01/24/2023] Open
Abstract
Objective Monosodium glutamate (MSG) is a food additive that has been shown to be toxic to rodents at high concentrations. The available studies in Drosophila melanogaster suggest that MSG toxicity depends on concentration and gender, thus the safety of MSG as a food enhancer still requires further investigation. We have documented impaired locomotor activity and altered oxidative stress markers in cockroaches co-exposed to methylmercury and monosodium glutamate (MSG). We herein examined the susceptibility of Nauphoeta cinerea to high and low concentrations (4% and 1%) of MSG, while monitoring the activities of acetylcholinesterase (AChE), as well as markers of oxidative stress and antioxidant activity over 30 days. Results There was no significant alteration in the parameters assessed at 1% MSG while 4% MSG caused an increase in the activity of reactive oxygen and nitrogen species, with a corresponding reduction in the activities of acetylcholinesterase, glutathione-S-transferase and catalase, suggesting the capacity of MSG to alter redox homeostasis in Nauphoeta cinerea.
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Affiliation(s)
- Blessing A Afolabi
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos 2600-Anexo, 90035-003, Porto Alegre, RS, Brazil. .,Departamento de Bioquímica e Biologia Molecular, Centro de Ciências Naturais e Exatas (CCNE), Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS, Brazil. .,Department of Biochemistry, Bowen University, Iwo, Osun State, Nigeria.
| | - Olawande C Olagoke
- Departamento de Bioquímica e Biologia Molecular, Centro de Ciências Naturais e Exatas (CCNE), Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS, Brazil
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Daur N, Zhang Y, Nadim F, Bucher D. Mutual Suppression of Proximal and Distal Axonal Spike Initiation Determines the Output Patterns of a Motor Neuron. Front Cell Neurosci 2019; 13:477. [PMID: 31708748 PMCID: PMC6819512 DOI: 10.3389/fncel.2019.00477] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Accepted: 10/10/2019] [Indexed: 11/13/2022] Open
Abstract
Axonal spike initiation at sites far from somatodendritic integration occurs in a range of systems, but its contribution to neuronal output activity is not well understood. We studied the interactions of distal and proximal spike initiation in an unmyelinated motor axon of the stomatogastric nervous system in the lobster, Homarus americanus. The peripheral axons of the pyloric dilator (PD) neurons generate tonic spiking in response to dopamine application. Centrally generated bursting activity and peripheral spike initiation had mutually suppressive effects. The two PD neurons and the electrically coupled oscillatory anterior burster (AB) neuron form the pacemaker ensemble of the pyloric central pattern generator, and antidromic invasion of central compartments by peripherally generated spikes caused spikelets in AB. Antidromic spikes suppressed burst generation in an activity-dependent manner: slower rhythms were diminished or completely disrupted, while fast rhythmic activity remained robust. Suppression of bursting was based on interference with the underlying slow wave oscillations in AB and PD, rather than a direct effect on spike initiation. A simplified multi-compartment circuit model of the pacemaker ensemble replicated this behavior. Antidromic activity disrupted slow wave oscillations by resetting the inward and outward current trajectories in each spike interval. Centrally generated bursting activity in turn suppressed peripheral spike initiation in an activity-dependent manner. Fast bursting eliminated peripheral spike initiation, while slower bursting allowed peripheral spike initiation to continue during the intervals between bursts. The suppression of peripheral spike initiation was associated with a small after-hyperpolarization in the sub-millivolt range. A realistic model of the PD axon replicated this behavior and showed that a sub-millivolt cumulative after-hyperpolarization across bursts was sufficient to eliminate peripheral spike initiation. This effect was based on the dynamic interaction between slow activity-dependent hyperpolarization caused by the Na+/K+-pump and inward rectification through the hyperpolarization-activated inward current, I h . These results demonstrate that interactions between different spike initiation sites based on spike propagation can shift the relative contributions of different types of activity in an activity-dependent manner. Therefore, distal axonal spike initiation can play an important role in shaping neural output, conditional on the relative level of centrally generated activity.
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Affiliation(s)
- Nelly Daur
- Federated Department of Biological Sciences, New Jersey Institute of Technology and Rutgers University-Newark, Newark, NJ, United States
| | - Yang Zhang
- Department of Mathematical Sciences, New Jersey Institute of Technology, Newark, NJ, United States
| | - Farzan Nadim
- Federated Department of Biological Sciences, New Jersey Institute of Technology and Rutgers University-Newark, Newark, NJ, United States.,Department of Mathematical Sciences, New Jersey Institute of Technology, Newark, NJ, United States
| | - Dirk Bucher
- Federated Department of Biological Sciences, New Jersey Institute of Technology and Rutgers University-Newark, Newark, NJ, United States
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7
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White RS, Spencer RM, Nusbaum MP, Blitz DM. State-dependent sensorimotor gating in a rhythmic motor system. J Neurophysiol 2017; 118:2806-2818. [PMID: 28814634 DOI: 10.1152/jn.00420.2017] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 08/14/2017] [Accepted: 08/14/2017] [Indexed: 11/22/2022] Open
Abstract
Sensory feedback influences motor circuits and/or their projection neuron inputs to adjust ongoing motor activity, but its efficacy varies. Currently, less is known about regulation of sensory feedback onto projection neurons that control downstream motor circuits than about sensory regulation of the motor circuit neurons themselves. In this study, we tested whether sensory feedback onto projection neurons is sensitive only to activation of a motor system, or also to the modulatory state underlying that activation, using the crab Cancer borealis stomatogastric nervous system. We examined how proprioceptor neurons (gastropyloric receptors, GPRs) influence the gastric mill (chewing) circuit neurons and the projection neurons (MCN1, CPN2) that drive the gastric mill rhythm. During gastric mill rhythms triggered by the mechanosensory ventral cardiac neurons (VCNs), GPR was shown previously to influence gastric mill circuit neurons, but its excitation of MCN1/CPN2 was absent. In this study, we tested whether GPR effects on MCN1/CPN2 are also absent during gastric mill rhythms triggered by the peptidergic postoesophageal commissure (POC) neurons. The VCN and POC pathways both trigger lasting MCN1/CPN2 activation, but their distinct influence on circuit feedback to these neurons produces different gastric mill motor patterns. We show that GPR excites MCN1 and CPN2 during the POC-gastric mill rhythm, altering their firing rates and activity patterns. This action changes both phases of the POC-gastric mill rhythm, whereas GPR only alters one phase of the VCN-gastric mill rhythm. Thus sensory feedback to projection neurons can be gated as a function of the modulatory state of an active motor system, not simply switched on/off with the onset of motor activity.NEW & NOTEWORTHY Sensory feedback influences motor systems (i.e., motor circuits and their projection neuron inputs). However, whether regulation of sensory feedback to these projection neurons is consistent across different versions of the same motor pattern driven by the same motor system was not known. We found that gating of sensory feedback to projection neurons is determined by the modulatory state of the motor system, and not simply by whether the system is active or inactive.
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Affiliation(s)
- Rachel S White
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | | | - Michael P Nusbaum
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Dawn M Blitz
- Department of Biology, Miami University, Oxford, Ohio; and
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Blitz DM, Pritchard AE, Latimer JK, Wakefield AT. Muscles innervated by a single motor neuron exhibit divergent synaptic properties on multiple time scales. ACTA ACUST UNITED AC 2017; 220:1233-1244. [PMID: 28104799 DOI: 10.1242/jeb.148908] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Accepted: 01/10/2017] [Indexed: 11/20/2022]
Abstract
Adaptive changes in the output of neural circuits underlying rhythmic behaviors are relayed to muscles via motor neuron activity. Presynaptic and postsynaptic properties of neuromuscular junctions can impact the transformation from motor neuron activity to muscle response. Further, synaptic plasticity occurring on the time scale of inter-spike intervals can differ between multiple muscles innervated by the same motor neuron. In rhythmic behaviors, motor neuron bursts can elicit additional synaptic plasticity. However, it is unknown whether plasticity regulated by the longer time scale of inter-burst intervals also differs between synapses from the same neuron, and whether any such distinctions occur across a physiological activity range. To address these issues, we measured electrical responses in muscles innervated by a chewing circuit neuron, the lateral gastric (LG) motor neuron, in a well-characterized small motor system, the stomatogastric nervous system (STNS) of the Jonah crab, Cancer borealisIn vitro and in vivo, sensory, hormonal and modulatory inputs elicit LG bursting consisting of inter-spike intervals of 50-250 ms and inter-burst intervals of 2-24 s. Muscles expressed similar facilitation measured with paired stimuli except at the shortest inter-spike interval. However, distinct decay time constants resulted in differences in temporal summation. In response to bursting activity, augmentation occurred to different extents and saturated at different inter-burst intervals. Further, augmentation interacted with facilitation, resulting in distinct intra-burst facilitation between muscles. Thus, responses of multiple target muscles diverge across a physiological activity range as a result of distinct synaptic properties sensitive to multiple time scales.
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Affiliation(s)
- Dawn M Blitz
- Department of Biology, Miami University, Oxford, OH 45056, USA
| | - Amy E Pritchard
- Department of Biology, Miami University, Oxford, OH 45056, USA
| | - John K Latimer
- Department of Biology, Miami University, Oxford, OH 45056, USA
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Neuromodulation to the Rescue: Compensation of Temperature-Induced Breakdown of Rhythmic Motor Patterns via Extrinsic Neuromodulatory Input. PLoS Biol 2015; 13:e1002265. [PMID: 26417944 PMCID: PMC4587842 DOI: 10.1371/journal.pbio.1002265] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Accepted: 08/28/2015] [Indexed: 11/30/2022] Open
Abstract
Stable rhythmic neural activity depends on the well-coordinated interplay of synaptic and cell-intrinsic conductances. Since all biophysical processes are temperature dependent, this interplay is challenged during temperature fluctuations. How the nervous system remains functional during temperature perturbations remains mostly unknown. We present a hitherto unknown mechanism of how temperature-induced changes in neural networks are compensated by changing their neuromodulatory state: activation of neuromodulatory pathways establishes a dynamic coregulation of synaptic and intrinsic conductances with opposing effects on neuronal activity when temperature changes, hence rescuing neuronal activity. Using the well-studied gastric mill pattern generator of the crab, we show that modest temperature increase can abolish rhythmic activity in isolated neural circuits due to increased leak currents in rhythm-generating neurons. Dynamic clamp-mediated addition of leak currents was sufficient to stop neuronal oscillations at low temperatures, and subtraction of additional leak currents at elevated temperatures was sufficient to rescue the rhythm. Despite the apparent sensitivity of the isolated nervous system to temperature fluctuations, the rhythm could be stabilized by activating extrinsic neuromodulatory inputs from descending projection neurons, a strategy that we indeed found to be implemented in intact animals. In the isolated nervous system, temperature compensation was achieved by stronger extrinsic neuromodulatory input from projection neurons or by augmenting projection neuron influence via bath application of the peptide cotransmitter Cancer borealis tachykinin-related peptide Ia (CabTRP Ia). CabTRP Ia activates the modulator-induced current IMI (a nonlinear voltage-gated inward current) that effectively acted as a negative leak current and counterbalanced the temperature-induced leak to rescue neuronal oscillations. Computational modelling revealed the ability of IMI to reduce detrimental leak-current influences on neuronal networks over a broad conductance range and indicated that leak and IMI are closely coregulated in the biological system to enable stable motor patterns. In conclusion, these results show that temperature compensation does not need to be implemented within the network itself but can be conditionally provided by extrinsic neuromodulatory input that counterbalances temperature-induced modifications of circuit-intrinsic properties. An electrophysiology and modelling study reveals how temperature can affect the balance of ionic conductances in neural circuits and how neuromodulators can compensate for detrimental temperature effects. All physiological processes are influenced by temperature. This is a particular problem for the nervous system, as temperature changes can disrupt the well-balanced flow of ions across the cell membrane necessary for maintaining nerve cell function. Possessing compensatory mechanisms that counterbalance detrimental temperature effects and maintain vital behaviors is especially important for poikilothermic animals, because they do not actively maintain their body temperature and can experience substantial temperature fluctuations. In this study, we analyze the mechanisms that allow the nervous system to maintain rhythmic activity over a range of different temperatures. To do so, we use the well-characterized central pattern generator of the stomatogastric nervous system of the crab that controls the motion of the gut. In this system, when experimentally isolated from the rest of the nervous system, even a small temperature increase can lead to termination of rhythmic activity due to a change in the balance of ionic conductances at elevated temperatures. However, the intact animal can compensate for these detrimental temperature effects. We demonstrate that such compensation can be achieved by restoring the balance of ionic conductance via an increase in neuromodulator release from projection neurons that control the motor circuits. We conclude that temperature compensation via neuromodulation may be a widespread phenomenon since it allows quick and flexible compensation of temperature influences on the nervous system.
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Follmann R, Rosa E, Stein W. Dynamics of signal propagation and collision in axons. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 92:032707. [PMID: 26465498 DOI: 10.1103/physreve.92.032707] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2015] [Indexed: 06/05/2023]
Abstract
Long-range communication in the nervous system is usually carried out with the propagation of action potentials along the axon of nerve cells. While typically thought of as being unidirectional, it is not uncommon for axonal propagation of action potentials to happen in both directions. This is the case because action potentials can be initiated at multiple "ectopic" positions along the axon. Two ectopic action potentials generated at distinct sites, and traveling toward each other, will collide. As neuronal information is encoded in the frequency of action potentials, action potential collision and annihilation may affect the way in which neuronal information is received, processed, and transmitted. We investigate action potential propagation and collision using an axonal multicompartment model based on the Hodgkin-Huxley equations. We characterize propagation speed, refractory period, excitability, and action potential collision for slow (type I) and fast (type II) axons. In addition, our studies include experimental measurements of action potential propagation in axons of two biological systems. Both computational and experimental results unequivocally indicate that colliding action potentials do not pass each other; they are reciprocally annihilated.
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Affiliation(s)
- Rosangela Follmann
- School of Biological Sciences, Illinois State University, Normal, Illinois 61790, USA
| | - Epaminondas Rosa
- Department of Physics, Illinois State University, Normal, Illinois 61790, USA
| | - Wolfgang Stein
- School of Biological Sciences, Illinois State University, Normal, Illinois 61790, USA
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11
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Goeritz ML, Bowers MR, Slepian B, Marder E. Neuropilar projections of the anterior gastric receptor neuron in the stomatogastric ganglion of the Jonah crab, Cancer borealis. PLoS One 2013; 8:e79306. [PMID: 24312448 PMCID: PMC3848923 DOI: 10.1371/journal.pone.0079306] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Accepted: 09/20/2013] [Indexed: 12/22/2022] Open
Abstract
Sensory neurons provide important feedback to pattern-generating motor systems. In the crustacean stomatogastric nervous system (STNS), feedback from the anterior gastric receptor (AGR), a muscle receptor neuron, shapes the activity of motor circuits in the stomatogastric ganglion (STG) via polysynaptic pathways involving anterior ganglia. The AGR soma is located in the dorsal ventricular nerve posterior to the STG and it has been thought that its axon passes through the STG without making contacts. Using high-resolution confocal microscopy with dye-filled neurons, we show here that AGR from the crab Cancer borealis also has local projections within the STG and that these projections form candidate contact sites with STG motor neurons or with descending input fibers from other ganglia. We develop and exploit a new masking method that allows us to potentially separate presynaptic and postsynaptic staining of synaptic markers. The AGR processes in the STG show diversity in shape, number of branches and branching structure. The number of AGR projections in the STG ranges from one to three simple to multiply branched processes. The projections come in close contact with gastric motor neurons and descending neurons and may also be electrically coupled to other neurons of the STNS. Thus, in addition to well described long-loop pathways, it is possible that AGR is involved in integration and pattern regulation directly in the STG.
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Affiliation(s)
- Marie L. Goeritz
- Biology Department and Volen Center, Brandeis University, Waltham, Massachusetts, United States of America
| | - Matthew R. Bowers
- Biology Department and Volen Center, Brandeis University, Waltham, Massachusetts, United States of America
| | - Brian Slepian
- Biology Department and Volen Center, Brandeis University, Waltham, Massachusetts, United States of America
| | - Eve Marder
- Biology Department and Volen Center, Brandeis University, Waltham, Massachusetts, United States of America
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12
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Abstract
In the isolated CNS, different modulatory inputs can enable one motor network to generate multiple output patterns. Thus far, however, few studies have established whether different modulatory inputs also enable a defined network to drive distinct muscle and movement patterns in vivo, much as they enable these distinctions in behavioral studies. This possibility is not a foregone conclusion, because additional influences present in vivo (e.g., sensory feedback, hormonal modulation) could alter the motor patterns. Additionally, rhythmic neuronal activity can be transformed into sustained muscle contractions, particularly in systems with slow muscle dynamics, as in the crab (Cancer borealis) stomatogastric system used here. We assessed whether two different versions of the biphasic (protraction, retraction) gastric mill (chewing) rhythm, triggered in the isolated stomatogastric system by the modulatory ventral cardiac neurons (VCNs) and postoesophageal commissure (POC) neurons, drive different muscle and movement patterns. One distinction between these rhythms is that the lateral gastric (LG) protractor motor neuron generates tonic bursts during the VCN rhythm, whereas its POC-rhythm bursts are divided into fast, rhythmic burstlets. Intracellular muscle fiber recordings and tension measurements show that the LG-innervated muscles retain the distinct VCN-LG and POC-LG neuron burst structures. Moreover, endoscope video recordings in vivo, during VCN-triggered and POC-triggered chewing, show that the lateral teeth protraction movements exhibit the same, distinct protraction patterns generated by LG in the isolated nervous system. Thus, the multifunctional nature of an identified motor network in the isolated CNS can be preserved in vivo, where it drives different muscle activity and movement patterns.
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Short-term synaptic plasticity compensates for variability in number of motor neurons at a neuromuscular junction. J Neurosci 2013; 32:16007-17. [PMID: 23136437 DOI: 10.1523/jneurosci.2584-12.2012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We studied how similar postsynaptic responses are maintained in the face of interindividual variability in the number of presynaptic neurons. In the stomatogastric ganglion of the lobster, Homarus americanus, the pyloric (PY) neurons exist in variable numbers across animals. We show that each individual fiber of the stomach muscles innervated by PY neurons received synaptic input from all neurons present. We performed intracellular recordings of excitatory junction potentials (EJPs) in the muscle fibers to determine the consequences of differences in the number of motor neurons. Despite the variability in neuron number, the compound electrical response of muscle fibers to natural bursting input was similar across individuals. The similarity of total synaptic activation was not due to differences in the spiking activity of individual motor neurons across animals with different numbers of PY neurons. The amplitude of a unitary EJP in response to a single spike in a single motor neuron also did not depend on the number of PY neurons present. Consequently, the compound EJP in response to a single stimulus that activated all motor axons present was larger in individuals with more PY neurons. However, when axons were stimulated with trains of pulses mimicking bursting activity, EJPs facilitated more in individuals with fewer PY neurons. After a few stimuli, this resulted in depolarizations similar to the ones in individuals with more PY neurons. We interpret our findings as evidence that compensatory or homeostatic regulatory mechanisms can act on short-term synaptic dynamics instead of absolute synaptic strength.
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McGaw IJ, Curtis DL. A review of gastric processing in decapod crustaceans. J Comp Physiol B 2012; 183:443-65. [DOI: 10.1007/s00360-012-0730-3] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2012] [Revised: 11/19/2012] [Accepted: 11/23/2012] [Indexed: 10/27/2022]
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Daur N, Diehl F, Mader W, Stein W. The stomatogastric nervous system as a model for studying sensorimotor interactions in real-time closed-loop conditions. Front Comput Neurosci 2012; 6:13. [PMID: 22435059 PMCID: PMC3303146 DOI: 10.3389/fncom.2012.00013] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2011] [Accepted: 02/25/2012] [Indexed: 11/13/2022] Open
Abstract
The perception of proprioceptive signals that report the internal state of the body is one of the essential tasks of the nervous system and helps to continuously adapt body movements to changing circumstances. Despite the impact of proprioceptive feedback on motor activity it has rarely been studied in conditions in which motor output and sensory activity interact as they do in behaving animals, i.e., in closed-loop conditions. The interaction of motor and sensory activities, however, can create emergent properties that may govern the functional characteristics of the system. We here demonstrate a method to use a well-characterized model system for central pattern generation, the stomatogastric nervous system, for studying these properties in vitro. We created a real-time computer model of a single-cell muscle tendon organ in the gastric mill of the crab foregut that uses intracellular current injections to control the activity of the biological proprioceptor. The resulting motor output of a gastric mill motor neuron is then recorded intracellularly and fed into a simple muscle model consisting of a series of low-pass filters. The muscle output is used to activate a one-dimensional Hodgkin-Huxley type model of the muscle tendon organ in real-time, allowing closed-loop conditions. Model properties were either hand tuned to achieve the best match with data from semi-intact muscle preparations, or an exhaustive search was performed to determine the best set of parameters. We report the real-time capabilities of our models, its performance and its interaction with the biological motor system.
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Affiliation(s)
- Nelly Daur
- Institute of Neurobiology, Ulm University Ulm, Germany
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16
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Abstract
Rhythmically active motor circuits can generate different activity patterns in response to different inputs. In most systems, however, it is not known whether the same neurons generate the underlying rhythm for each different pattern. Thus far, information regarding the degree of conservation of rhythm generator neurons is limited to a few pacemaker-driven circuits, in most of which the core rhythm generator is unchanged across different output patterns. We are addressing this issue in the network-driven, gastric mill (chewing) circuit in the crab stomatogastric nervous system. We first establish that distinct gastric mill motor patterns are triggered by separate stimulation of two extrinsic input pathways, the ventral cardiac neurons (VCNs) and postoesophageal commissure (POC) neurons. A prominent feature that distinguishes these gastric mill motor patterns is the LG (lateral gastric) protractor motor neuron activity pattern, which is tonic during the VCN rhythm and exhibits fast rhythmic bursting during the POC rhythm. These two motor patterns also differed in their cycle period and some motor neuron phase relationships, duty cycles, and burst durations. Despite the POC and VCN motor patterns being distinct, rhythm generation during each motor pattern required the activity of the same two, reciprocally inhibitory gastric mill neurons [LG, Int1 (interneuron 1)]. Specifically, reversibly hyperpolarizing LG or Int1, but no other gastric mill neuron, delayed the start of the next gastric mill cycle until after the imposed hyperpolarization. Thus, the same circuit neurons can comprise the core rhythm generator during different versions of a network-driven rhythmic motor pattern.
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Stein W, Städele C, Andras P. Optical imaging of neurons in the crab stomatogastric ganglion with voltage-sensitive dyes. J Vis Exp 2011:2567. [PMID: 21490564 PMCID: PMC3197313 DOI: 10.3791/2567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Voltage-sensitive dye imaging of neurons is a key methodology for the understanding of how neuronal networks are organised and how the simultaneous activity of participating neurons leads to the emergence of the integral functionality of the network. Here we present the methodology of application of this technique to identified pattern generating neurons in the crab stomatogastric ganglion. We demonstrate the loading of these neurons with the fluorescent voltage-sensitive dye Di-8-ANEPPQ and we show how to image the activity of dye loaded neurons using the MiCAM02 high speed and high resolution CCD camera imaging system. We demonstrate the analysis of the recorded imaging data using the BVAna imaging software associated with the MiCAM02 imaging system. The simultaneous voltage-sensitive dye imaging of the detailed activity of multiple neurons in the crab stomatogastric ganglion applied together with traditional electrophysiology techniques (intracellular and extracellular recordings) opens radically new opportunities for the understanding of how central pattern generator neural networks work.
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Hedrich UBS, Diehl F, Stein W. Gastric and pyloric motor pattern control by a modulatory projection neuron in the intact crab Cancer pagurus. J Neurophysiol 2011; 105:1671-80. [PMID: 21325688 DOI: 10.1152/jn.01105.2010] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Neuronal release of modulatory substances provides motor pattern generating circuits with a high degree of flexibility. In vitro studies have characterized the actions of modulatory projection neurons in great detail in the stomatogastric nervous system, a model system for neuromodulatory influences on central pattern generators. Less is known about the activities and actions of modulatory neurons in fully functional and richly modulated network settings, i.e., in intact animals. It is also unknown whether their activities contribute to the motor patterns in different behavioral conditions. Here, we show for the first time the activity and effects of the well-characterized modulatory projection neuron 1 (MCN1) in vivo and compare them to in vitro conditions. MCN1 was always spontaneously active, typically in a rhythmic fashion with its firing being interrupted by ascending inhibitions from the pyloric motor circuit. Its activity contributed to pyloric motor activity, because 1) the cycle period of the motor pattern correlated with MCN1 firing frequency and 2) stimulating MCN1 shortened the cycle period while 3) lesioning of the MCN1 axon reduced motor activity. In addition, gastric mill motor activity was elicited for the duration of the stimulation. Chemosensory stimulation of the antennae moved MCN1 away from baseline activity by increasing its firing frequency. Following this increase, a gastric mill rhythm was elicited and the pyloric cycle period decreased. Lesioning the MCN1 axon prevented these effects. Thus modulatory projection neurons such as MCN1 can control the motor output in vivo, and they participate in the processing of exteroceptive sensory information in behaviorally relevant conditions.
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Affiliation(s)
- Ulrike B S Hedrich
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, Tübingen, Germany
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Stein W, Städele C, Andras P. Single-sweep voltage-sensitive dye imaging of interacting identified neurons. J Neurosci Methods 2010; 194:224-34. [PMID: 20969892 DOI: 10.1016/j.jneumeth.2010.10.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2010] [Revised: 10/08/2010] [Accepted: 10/08/2010] [Indexed: 11/24/2022]
Abstract
The simultaneous recording of many individual neurons is fundamental to understanding the integral functionality of neural systems. Imaging with voltage-sensitive dyes (VSDs) is a key approach to achieve this goal and a promising technique to supplement electrophysiological recordings. However, the lack of connectivity maps between imaged neurons and the requirement of averaging over repeated trials impede functional interpretations. Here we demonstrate fast, high resolution and single-sweep VSD imaging of identified and synaptically interacting neurons. We show for the first time the optical recording of individual action potentials and mutual inhibitory synaptic input of two key players in the well-characterized pyloric central pattern generator in the crab stomatogastric ganglion (STG). We also demonstrate the presence of individual synaptic potentials from other identified circuit neurons. We argue that imaging of neural networks with identifiable neurons with well-known connectivity, like in the STG, is crucial for the understanding of emergence of network functionality.
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Affiliation(s)
- Wolfgang Stein
- Institute of Neurobiology, Ulm University, D-89069 Ulm, Germany
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20
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Stein W, Andras P. Light-induced effects of a fluorescent voltage-sensitive dye on neuronal activity in the crab stomatogastric ganglion. J Neurosci Methods 2010; 188:290-4. [PMID: 20226813 DOI: 10.1016/j.jneumeth.2010.03.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2010] [Revised: 03/01/2010] [Accepted: 03/05/2010] [Indexed: 11/28/2022]
Abstract
Optical imaging being one of the cutting-edge methods for the investigation of neural activity, it is very important to understand the mechanisms of how dye molecules work and the range of side effects that they may induce. In particular, it is very important to reveal potential toxic effects and effects impairing the functioning of the investigated neural system. Here, we investigate the effects of illumination in the presence of the commonly used di-4-ANEPPS voltage-sensitive dye on the rhythmic motor pattern generated by the pyloric central pattern generator in the crab stomatogastric nervous system, a model system for motor pattern generation. We report that the dye allows long recording sessions with little bleaching and no obvious damage to the pyloric rhythm. Yet, exciting illumination induced a temporary and reversible change in the phase relationship of the pyloric motor neurons and a concomitant speed-up of the rhythm. The effect was specific to the excitation wavelength of di-4-ANEPPS and only obtained when the neuropile and cell bodies were illuminated. Thus, di-4-ANEPPS acts as a photo-switch that causes a quick and reversible change in the phase relationship of the motor neurons, but no permanent impairment of neuronal function. It may thus also be used as a means to study the maintenance of phase relationships in rhythmic motor patterns.
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Affiliation(s)
- Wolfgang Stein
- Institute of Neurobiology, Ulm University, Ulm D-89069, Germany.
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Modulation of stomatogastric rhythms. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2009; 195:989-1009. [PMID: 19823843 DOI: 10.1007/s00359-009-0483-y] [Citation(s) in RCA: 111] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2009] [Revised: 09/15/2009] [Accepted: 09/20/2009] [Indexed: 12/15/2022]
Abstract
Neuromodulation by peptides and amines is a primary source of plasticity in the nervous system as it adapts the animal to an ever-changing environment. The crustacean stomatogastric nervous system is one of the premier systems to study neuromodulation and its effects on motor pattern generation at the cellular level. It contains the extensively modulated central pattern generators that drive the gastric mill (chewing) and pyloric (food filtering) rhythms. Neuromodulators affect all stages of neuronal processing in this system, from membrane currents and synaptic transmission in network neurons to the properties of the effector muscles. The ease with which distinct neurons are identified and their activity is recorded in this system has provided considerable insight into the mechanisms by which neuromodulators affect their target cells and modulatory neuron function. Recent evidence suggests that neuromodulators are involved in homeostatic processes and that the modulatory system itself is under modulatory control, a fascinating topic whose surface has been barely scratched. Future challenges include exploring the behavioral conditions under which these systems are activated and how their effects are regulated.
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Hedrich UBS, Smarandache CR, Stein W. Differential activation of projection neurons by two sensory pathways contributes to motor pattern selection. J Neurophysiol 2009; 102:2866-79. [PMID: 19741101 DOI: 10.1152/jn.00618.2009] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Sensorimotor integration is known to occur at the level of motor circuits as well as in upstream interneurons that regulate motor activity. Here we show, using the crab stomatogastric nervous system (STNS) as a model, that different sensory systems affect the same set of projection neurons. However, they have qualitatively different effects on their activities (excitation vs. inhibition), and these differences contribute to the selection of motor patterns from multifunctional circuits. We compare the actions of the proprioceptive anterior gastric receptor (AGR) and the inferior ventricular (IV) neurons, which relay chemosensory information from the brain to the STNS, on modulatory commissural neurons 1 and 5 (MCN1 and MCN5) and commissural projection neuron 2 (CPN2) and their resulting actions on the gastric mill central pattern generating circuit in the stomatogastric ganglion. When stimulated, AGR and the IV neurons affect all three projection neurons but elicit distinct gastric mill rhythms. The effects of both sensory pathways on the projection neurons differ in the type of excitation provided to CPN2 and MCN5 (electrical vs. chemical) and the effect on MCN1 (direct inhibition by AGR vs. polysynaptic excitation by the IV neurons). The latter is functionally important because a restoration of MCN1 activity during the AGR rhythm made it more similar to that elicited by IV neuron stimulation. Our results thus support the hypothesis that sensory pathways activate different combinations of projection neurons to select distinct outputs from the same neuronal circuit.
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Coordination of rhythmic motor activity by gradients of synaptic strength in a neural circuit that couples modular neural oscillators. J Neurosci 2009; 29:9351-60. [PMID: 19625525 DOI: 10.1523/jneurosci.1744-09.2009] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Synchronization of distributed neural circuits is required for many behavioral tasks, but the mechanisms that coordinate these circuits are largely unknown. The modular local circuits that control crayfish swimmerets are distributed in four segments of the CNS, but when the swimmeret system is active their outputs are synchronized with a stable intersegmental phase difference of 0.25, an example of metachronal synchronization (Izhikevich, 2007). In each module, coordinating neurons encode detailed information about each cycle of the module's motor output as bursts of spikes, and their axons conduct this information to targets in other segments. This information is both necessary and sufficient for normal intersegmental coordination. In a comprehensive set of recordings, we mapped the synaptic connections of two types of coordinating neurons onto their common target neurons in other segments. Both types of coordinating axons caused large, brief EPSPs in their targets. The shape indices of these EPSPs are tuned to transmit the information from each axon precisely. In each target neuron's own module, these bursts of EPSPs modified the phase of the module's motor output. Each axon made its strongest synapse onto the target neuron in the nearest neighboring segment. Its synapses onto homologous targets in more remote segments were progressively weaker. Each target neuron decodes information from several coordinating axons, and the strengths of their synapses differ systematically. These differences in synaptic strength weight information from each segment differently, which might account for features of the system's characteristic metachronal synchronization.
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Daur N, Nadim F, Stein W. Regulation of motor patterns by the central spike-initiation zone of a sensory neuron. Eur J Neurosci 2009; 30:808-22. [PMID: 19686469 DOI: 10.1111/j.1460-9568.2009.06866.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Sensory feedback from muscles and peripheral sensors acts to initiate, tune or reshape motor activity according to the state of the body. Yet, sensory neurons often show low levels of activity even in the absence of sensory input. Here we examine the functional role of spontaneous low-frequency activity of such a sensory neuron. The anterior gastric receptor (AGR) is a muscle-tendon organ in the crab stomatogastric nervous system whose phasic activity shapes the well-characterized gastric mill (chewing) and pyloric (filtering) motor rhythms. Phasic activity is driven by a spike-initiation zone near the innervated muscle. We demonstrate that AGR possesses a second spike-initiation zone, which is located spatially distant from the innervated muscle in a central section of the axon. This initiation zone generates tonic activity and is responsible for the spontaneous activity of AGR in vivo, but does not code sensory information. Rather, it is sensitive to the neuromodulator octopamine. A computational model indicates that the activity at this initiation zone is not caused by excitatory input from another neuron, but generated intrinsically. This tonic activity is functionally relevant, because it modifies the activity state of the gastric mill motor circuit and changes the pyloric rhythm. The sensory function of AGR is not impaired as phasic activity suppresses spiking at the central initiation zone. Our results thus demonstrate that sensory neurons are not mere reporters of sensory signals. Neuromodulators can elicit non-sensory coding activity in these neurons that shapes the state of the motor system.
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Affiliation(s)
- Nelly Daur
- Institute of Neurobiology, Ulm University, Ulm, Germany
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Hedrich UBS, Stein W. Characterization of a descending pathway: activation and effects on motor patterns in the brachyuran crustacean stomatogastric nervous system. J Exp Biol 2008; 211:2624-37. [DOI: 10.1242/jeb.019711] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARYThe regulation of motor patterns by higher-order neuronal centers ensures appropriate motor function and behavior, but only a few studies have characterized this regulation at the cellular level. Here, we address motor pattern regulation in the stomatogastric nervous system (STNS) of the crab Cancer pagurus. This easily accessible model system is an extension of the central nervous system and contains the motor circuits that generate the rhythmic motor patterns for ingestion (esophageal rhythm) and processing of food (gastric mill and pyloric rhythms).We have documented the actions of two identified neurons located in the brain on the STNS motor circuits. We show that these neurons provide exteroceptive chemosensory information to the motor circuits and we outline their axonal projection patterns, their firing activity and their effects on three motor patterns. Backfill stainings and activity measurements in vivo and in vitro show that two neurons located in cluster 17 of the brain project via the inferior ventricular (IV) nerve to the STNS. These IV neurons started to burst rhythmically when chemosensory stimuli were applied to the first antennae. When rhythmically activated in vitro, gastric mill rhythms were elicited or, if already active,entrained by the IV neuron activity. In addition, IV neuron stimulation excited the esophageal motor neuron and inhibited several pyloric neurons such that the timing of the IV neuron activity was imposed on all motor rhythms. The IV neurons were thus capable of synchronizing the activities of different motor circuits, which demonstrates the regulation of motor patterns by higher-order neuronal centers.
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Affiliation(s)
| | - Wolfgang Stein
- Institute of Neurobiology, Ulm University, D-89069 Ulm, Germany
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Smarandache CR, Daur N, Hedrich UBS, Stein W. Regulation of motor pattern frequency by reversals in proprioceptive feedback. Eur J Neurosci 2008; 28:460-74. [DOI: 10.1111/j.1460-9568.2008.06357.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Smarandache CR, Stein W. Sensory-induced modification of two motor patterns in the crab, Cancer pagurus. ACTA ACUST UNITED AC 2007; 210:2912-22. [PMID: 17690240 DOI: 10.1242/jeb.006874] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Sensory input is pervasive among motor networks and continuously adapts motor patterns to changing circumstances. To elucidate common principles of sensorimotor integration, it is beneficial to characterize sensory influences on motor network operation and compare these influences between species. To facilitate such comparison, we have studied the influence of the anterior gastric receptor (AGR) - a proprioceptor that has been characterized in detail in two lobster species - on the pyloric (filtering of food) and gastric mill (chewing of food) motor patterns in the crab Cancer pagurus. AGR has a bipolar cell body in the stomatogastric ganglion; it was activated by tension increase in gastric mill powerstroke muscles. While two spike initiation zones accounted for its spontaneous activity, active membrane properties (sag potentials, spike frequency adaptation) contributed to the AGR response to current injections. When activated, AGR diminished spike activities in two pyloric motor neurons and prolonged the pyloric cycle period. Furthermore, AGR excited gastric mill protractor neurons, inhibited the retractor neuron and evoked phase-independent resetting of the gastric mill rhythm. Repetitive spike trains entrained the rhythm to both longer and shorter cycle periods. All AGR actions seemed to be mediated via at least two premotor projection neurons in the spatially distant commissural ganglia. The response of the gastric mill neurons was independent of AGR firing frequency. Our results suggest that homologous proprioceptors can elicit similar effects on motor patterns while utilizing different mechanisms. This work thus provides an initial framework for future studies to determine underlying common principles.
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