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Eve Marder - One of the best experts on this subject based on the ideXlab platform.
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phase maintenance in a rhythmic Motor Pattern during temperature changes in vivo
Journal of Neurophysiology, 2014Co-Authors: Wafa Soofi, Wolfgang Stein, Eve Marder, Marie L Goeritz, Tilman J Kispersky, Astrid A PrinzAbstract:Central-Pattern-generating neural circuits function reliably throughout an animal's life, despite constant molecular turnover and environmental perturbations. Fluctuations in temperature pose a problem to the nervous systems of poikilotherms because their body temperature follows the ambient temperature, thus affecting the temperature-dependent dynamics of various subcellular components that constitute neuronal circuits. In the crustacean stomatogastric nervous system, the pyloric circuit produces a triphasic rhythm comprising the output of the pyloric dilator, lateral pyloric, and pyloric constrictor neurons. In vitro, the phase relationships of these neurons are maintained over a fourfold change in pyloric frequency as temperature increases from 7°C to 23°C. To determine whether these temperature effects are also found in intact crabs, in the presence of sensory feedback and neuromodulator-rich environments, we measured the temperature dependence of the pyloric frequency and phases in vivo by implanting extracellular electrodes into Cancer borealis and Cancer pagurus and shifting tank water temperature from 11°C to 26°C. Pyloric frequency in the intact crab increased significantly with temperature (Q10 = 2–2.5), while pyloric phases were generally conserved. For a subset of the C. borealis experiments, animals were subsequently dissected and the stomatogastric ganglion subjected to a similar temperature ramp in vitro. We found that the maximal frequency attained at high temperatures in vivo is lower than it is under in vitro conditions. Our results demonstrate that, over a wide temperature range, the phases of the pyloric rhythm in vivo are generally preserved, but that the frequency range is more restricted than it is in vitro.
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precise temperature compensation of phase in a rhythmic Motor Pattern
PLOS Biology, 2010Co-Authors: Lamont S Tang, Marie L Goeritz, Jonathan S Caplan, Adam L Taylor, Mehmet Fisek, Eve MarderAbstract:Most animal species are cold-blooded, and their neuronal circuits must maintain function despite environmental temperature fluctuations. The central Pattern generating circuits that produce rhythmic Motor Patterns depend on the orderly activation of circuit neurons. We describe the effects of temperature on the pyloric rhythm of the stomatogastric ganglion of the crab, Cancer borealis. The pyloric rhythm is a triphasic Motor Pattern in which the Pyloric Dilator (PD), Lateral Pyloric (LP), and Pyloric (PY) neurons fire in a repeating sequence. While the frequency of the pyloric rhythm increased about 4-fold (Q10∼2.3) as the temperature was shifted from 7°C to 23°C, the phase relationships of the PD, LP, and PY neurons showed almost perfect temperature compensation. The Q10's of the input conductance, synaptic currents, transient outward current (IA), and the hyperpolarization-activated inward current (Ih), all of which help determine the phase of LP neuron activity, ranged from 1.8 to 4. We studied the effects of temperature in >1,000 computational models (with different sets of maximal conductances) of a bursting neuron and the LP neuron. Many bursting models failed to monotonically increase in frequency as temperature increased. Temperature compensation of LP neuron phase was facilitated when model neurons' currents had Q10's close to 2. Together, these data indicate that although diverse sets of maximal conductances may be found in identified neurons across animals, there may be strong evolutionary pressure to restrict the Q10's of the processes that contribute to temperature compensation of neuronal circuits.
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animal to animal variability in Motor Pattern production in adults and during growth
The Journal of Neuroscience, 2005Co-Authors: Dirk Bucher, Astrid A Prinz, Eve MarderAbstract:Which features of network output are well preserved during growth of the nervous system and across different preparations of the same size? To address this issue, we characterized the pyloric rhythms generated by the stomatogastric nervous systems of 99 adult and 12 juvenile lobsters (Homarus americanus). Anatomical studies of single pyloric network neurons and of the whole stomatogastric ganglion (STG) showed that the STG and its neurons grow considerably from juvenile to adult. Despite these changes in size, intracellularly recorded membrane potential waveforms of pyloric network neurons and the phase relationships in the pyloric rhythm were very similar between juvenile and adult preparations. Across adult preparations, the cycle period and number of spikes per burst were not tightly maintained, but the mean phase relationships were independent of the period of the rhythm and relatively tightly maintained across preparations. We interpret this as evidence for homeostatic regulation of network activity.
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Motor Pattern generation.
Current opinion in neurobiology, 2000Co-Authors: Eve MarderAbstract:Recent work on the circuits that generate rhythmic movements illustrates the role of cotransmitter complement in Motor Pattern selection and demonstrates that many principles first established in invertebrates also hold in vertebrates. Major new areas of investigation include the development of central Pattern generating networks, and the use of mouse mutants.
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Principles of rhythmic Motor Pattern generation
Physiological reviews, 1996Co-Authors: Eve Marder, Ronald L. CalabreseAbstract:Rhythmic movements are produced by central Pattern-generating networks whose output is shaped by sensory and neuromodulatory inputs to allow the animal to adapt its movements to changing needs. This review discusses cellular, circuit, and computational analyses of the mechanisms underlying the generation of rhythmic movements in both invertebrate and vertebrate nervous systems. Attention is paid to exploring the mechanisms by which synaptic and cellular processes interact to play specific roles in shaping Motor Patterns and, consequently, movement.
Wolfgang Stein - One of the best experts on this subject based on the ideXlab platform.
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phase maintenance in a rhythmic Motor Pattern during temperature changes in vivo
Journal of Neurophysiology, 2014Co-Authors: Wafa Soofi, Wolfgang Stein, Eve Marder, Marie L Goeritz, Tilman J Kispersky, Astrid A PrinzAbstract:Central-Pattern-generating neural circuits function reliably throughout an animal's life, despite constant molecular turnover and environmental perturbations. Fluctuations in temperature pose a problem to the nervous systems of poikilotherms because their body temperature follows the ambient temperature, thus affecting the temperature-dependent dynamics of various subcellular components that constitute neuronal circuits. In the crustacean stomatogastric nervous system, the pyloric circuit produces a triphasic rhythm comprising the output of the pyloric dilator, lateral pyloric, and pyloric constrictor neurons. In vitro, the phase relationships of these neurons are maintained over a fourfold change in pyloric frequency as temperature increases from 7°C to 23°C. To determine whether these temperature effects are also found in intact crabs, in the presence of sensory feedback and neuromodulator-rich environments, we measured the temperature dependence of the pyloric frequency and phases in vivo by implanting extracellular electrodes into Cancer borealis and Cancer pagurus and shifting tank water temperature from 11°C to 26°C. Pyloric frequency in the intact crab increased significantly with temperature (Q10 = 2–2.5), while pyloric phases were generally conserved. For a subset of the C. borealis experiments, animals were subsequently dissected and the stomatogastric ganglion subjected to a similar temperature ramp in vitro. We found that the maximal frequency attained at high temperatures in vivo is lower than it is under in vitro conditions. Our results demonstrate that, over a wide temperature range, the phases of the pyloric rhythm in vivo are generally preserved, but that the frequency range is more restricted than it is in vitro.
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Regulation of Motor Pattern frequency by reversals in proprioceptive feedback.
The European journal of neuroscience, 2008Co-Authors: Carmen R. Smarandache, Nelly Daur, Ulrike B. S. Hedrich, Wolfgang SteinAbstract:Proprioceptive sensory feedback has important functions for Motor Pattern generation in which phasic negative and positive feedback is used to coordinate neural and musculoskeletal dynamics. Whether and how feedback sign regulates the Motor Patterns in behaviorally relevant closed-loop conditions has not been fully elucidated. We characterized the feedback provided by the anterior gastric receptor (AGR), a muscle tendon organ in the stomatogastric nervous system of the crab Cancer pagurus, to the gastric mill Motor Pattern in intact animals. AGR innervates the protractor muscles and was activated either during the protraction or retraction phase of the rhythm. Experiments with neuromuscular preparations imply that this was due to isometric contractions of the protractor muscles and their passive stretch by the antagonistic retractor muscles. As AGR excited the protractors and inhibited the retractors independently of the timing of its activation, the timing switch changed AGR feedback from positive to negative. We tested the effects of this change in feedback sign on the Motor Pattern in the isolated nervous system by activating AGR at the corresponding phases of the rhythm, using intracellular current injection. When AGR was activated during the protractor phase and provided positive feedback, it prolonged the burst activities of protractor and retractor neurons and slowed ongoing rhythms. When activated during the retraction phase and thus provided negative feedback, burst durations decreased and the rhythm cycle frequency increased. Our study thus shows that the cycle frequency of centrally generated activity Patterns can be regulated by switching the sign of phasic proprioceptive feedback.
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divergent co transmitter actions underlie Motor Pattern activation by a modulatory projection neuron
European Journal of Neuroscience, 2007Co-Authors: Nicholas D Delong, Wolfgang Stein, Debra E Wood, Michael P NusbaumAbstract:Co-transmission is a common means of neuronal communication, but its consequences for neuronal signaling within a defined neuronal circuit remain unknown in most systems. We are addressing this issue in the crab stomatogastric nervous system by characterizing how the identified modulatory commissural neuron (MCN)1 uses its co-transmitters to activate the gastric mill (chewing) rhythm in the stomatogastric ganglion (STG). MCN1 contains gamma-aminobutyric acid (GABA) plus the peptides proctolin and Cancer borealis tachykinin-related peptide Ia (CabTRP Ia), which it co-releases during the retractor phase of the gastric mill rhythm to influence both retractor and protractor neurons. By focally applying each MCN1 co-transmitter and pharmacologically manipulating each co-transmitter action during MCN1 stimulation, we found that MCN1 has divergent co-transmitter actions on the gastric mill central Pattern generator (CPG), which includes the neurons lateral gastric (LG) and interneuron 1 (Int1), plus the STG terminals of MCN1 (MCN1(STG)). MCN1 used only CabTRP Ia to influence LG, while it used only GABA to influence Int1 and the contralateral MCN1(STG). These MCN1 actions caused a slow excitation of LG, a fast excitation of Int1 and a fast inhibition of MCN1(STG). MCN1-released proctolin had no direct influence on the gastric mill CPG, although it likely indirectly regulates this CPG via its influence on the pyloric rhythm. MCN1 appeared to have no ionotropic actions on the gastric mill follower Motor neurons, but it did use proctolin and/or CabTRP Ia to excite them. Thus, a modulatory projection neuron can elicit rhythmic Motor activity by using distinct co-transmitters, with different time courses of action, to simultaneously influence different CPG neurons.
Ronald L. Calabrese - One of the best experts on this subject based on the ideXlab platform.
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Variation in Motor output and Motor performance in a centrally generated Motor Pattern
Journal of Neurophysiology, 2014Co-Authors: Angela Wenning, Brian J. Norris, Anca Doloc-mihu, Ronald L. CalabreseAbstract:Central Pattern generators (CPGs) produce Motor Patterns that ultimately drive Motor outputs. We studied how functional Motor performance is achieved, specifically, whether the variation seen in Motor Patterns is reflected in Motor performance and whether fictive Motor Patterns differ from those in vivo. We used the leech heartbeat system in which a bilaterally symmetrical CPG coordinates segmental heart Motor neurons and two segmented heart tubes into two mutually exclusive coordination modes: rear-to-front peristaltic on one side and nearly synchronous on the other, with regular side-to-side switches. We assessed individual variability of the Motor Pattern and the beat Pattern in vivo. To quantify the beat Pattern we imaged intact adults. To quantify the phase relations between Motor neurons and heart constrictions we recorded extracellularly from two heart Motor neurons and movement from the corresponding heart segments in minimally dissected leeches. Variation in the Motor Pattern was reflected in Motor performance only in the peristaltic mode, where larger intersegmental phase differences in the Motor neurons resulted in larger phase differences between heart constrictions. Fictive Motor Patterns differed from those in vivo only in the synchronous mode, where intersegmental phase differences in vivo had a larger front-to-rear bias and were more constrained. Additionally, load-influenced constriction timing might explain the amplification of the phase differences between heart segments in the peristaltic mode and the higher variability in Motor output due to body shape assumed in this soft-bodied animal. The Motor Pattern determines the beat Pattern, peristaltic or synchronous, but heart mechanics influence the phase relations achieved.
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correlated conductance parameters in leech heart Motor neurons contribute to Motor Pattern formation
PLOS ONE, 2013Co-Authors: Damon G Lamb, Ronald L. CalabreseAbstract:Neurons can have widely differing intrinsic membrane properties, in particular the density of specific conductances, but how these contribute to characteristic neuronal activity or Pattern formation is not well understood. To explore the relationship between conductances, and in particular how they influence the activity of Motor neurons in the well characterized leech heartbeat system, we developed a new multi-compartmental Hodgkin-Huxley style leech heart Motor neuron model. To do so, we evolved a population of model instances, which differed in the density of specific conductances, capable of achieving specific output activity targets given an associated input Pattern. We then examined the sensitivity of measures of output activity to conductances and how the model instances responded to hyperpolarizing current injections. We found that the strengths of many conductances, including those with differing dynamics, had strong partial correlations and that these relationships appeared to be linked by their influence on heart Motor neuron activity. Conductances that had positive correlations opposed one another and had the opposite effects on activity metrics when perturbed whereas conductances that had negative correlations could compensate for one another and had similar effects on activity metrics.
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contribution of motoneuron intrinsic properties to fictive Motor Pattern generation
Journal of Neurophysiology, 2011Co-Authors: Terrence Michael Wright, Ronald L. CalabreseAbstract:Previously, we reported a canonical ensemble model of the heart motoneurons that underlie heartbeat in the medicinal leech. The model motoneurons contained a minimal set of electrical intrinsic properties and received a synaptic input Pattern based on measurements performed in the living system. Although the model captured the synchronous and peristaltic Motor Patterns observed in the living system, it did not match quantitatively the Motor output observed. Because the model motoneurons had minimal intrinsic electrical properties, the mismatch between model and living system suggests a role for additional intrinsic properties in generating the Motor Pattern. We used the dynamic clamp to test this hypothesis. We introduced the same segmental input Pattern used in the model to motoneurons isolated pharmacologically from their endogenous input in the living system. We show that, although the segmental input Pattern determines the segmental phasing differences observed in motoneurons, the intrinsic properties of the motoneurons play an important role in determining their phasing, particularly when receiving the synchronous input Pattern. We then used trapezoidal input waveforms to show that the intrinsic properties present in the living system promote phase advances compared with our model motoneurons. Electrical coupling between heart motoneurons also plays a role in shaping motoneuron output by synchronizing the activity of the motoneurons within a segment. These experiments provide a direct assessment of how motoneuron intrinsic properties interact with their preMotor Pattern of synaptic drive to produce rhythmic output.
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a central Pattern generator producing alternative outputs phase relations of leech heart Motor neurons with respect to preMotor synaptic input
Journal of Neurophysiology, 2007Co-Authors: Brian J. Norris, Angela Wenning, Adam L Weaver, Paul S Garcia, Ronald L. CalabreseAbstract:The central Pattern generator (CPG) for heartbeat in leeches consists of seven identified pairs of segmental heart interneurons and one unidentified pair. Four of the identified pairs and the unidentified pair of interneurons make inhibitory synaptic connections with segmental heart Motor neurons. The CPG produces a side-to-side asymmetric Pattern of intersegmental coordination among ipsilateral preMotor interneurons corresponding to a similarly asymmetric fictive Motor Pattern in heart Motor neurons, and asymmetric constriction Pattern of the two tubular hearts: synchronous and peristaltic. Using extracellular techniques, we recorded, in 61 isolated nerve cords, the activity of Motor neurons in conjunction with the phase reference preMotor heart interneuron, HN(4), and another preMotor interneuron that allowed us to assess the coordination mode. These data were then coupled with a previous description of the temporal Pattern of preMotor interneuron activity in the two coordination modes to synthesize a global phase diagram for the known elements of the CPG and the entire Motor neuron ensemble. These average data reveal the stereotypical side-to-side asymmetric Patterns of intersegmental coordination among the Motor neurons and show how this Pattern meshes with the activity Pattern of preMotor interneurons. Analysis of animal-to-animal variability in this coordination indicates that the intersegmental phase progression of Motor neuron activity in the midbody in the peristaltic coordination mode is the most stereotypical feature of the fictive Motor Pattern. Bilateral recordings from Motor neurons corroborate the main features of the asymmetric Motor Pattern.
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Heartbeat Control in Leeches. II. Fictive Motor Pattern
Journal of neurophysiology, 2003Co-Authors: Angela Wenning, Andrew A. V. Hill, Ronald L. CalabreseAbstract:The rhythmic beating of the tube-like hearts in the medicinal leech is driven and coordinated by rhythmic activity in segmental heart Motor neurons. The Motor neurons are controlled by rhythmic inhibitory input from a network of heart interneurons that compose the heartbeat central Pattern generator. In the preceding paper, we described the constriction Pattern of the hearts in quiescent intact animals and showed that one heart constricts in a rear-to-front wave (peristaltic coordination mode), while the other heart constricts in near unison over its length (synchronous coordination mode) and that they regularly switch coordination modes. Here we analyze intersegmental and side-to-side-coordination of the fictive Motor Pattern for heartbeat in denervated nerve cords. We show that the intersegmental phase relations among heart Motor neurons in both coordination modes are independent of heartbeat period. This finding enables us to combine data from different experiments to form a detailed analysis of the relative phases, duty cycle, and intraburst spike frequency of the bursts of the segmental heart Motor neurons. The fictive Motor Pattern and the constriction Pattern seen in intact leeches closely match in their intersegmental and side-to-side coordination, indicating that sensory feedback is not necessary for properly phased intersegmental coordination. Moreover, the regular switches in coordination mode of the fictive Motor Pattern mimic those seen in intact animals indicating that these switches likely arise by a central mechanism.
James W Dennis - One of the best experts on this subject based on the ideXlab platform.
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the ubr 1 ubiquitin ligase regulates glutamate metabolism to generate coordinated Motor Pattern in caenorhabditis elegans
PLOS Genetics, 2018Co-Authors: Jythosna Chitturi, Wesley Hung, Anas Abdel M Rahman, John A Calarco, Renee Baran, Xun Huang, James W Dennis, Maria A LimAbstract:UBR1 is an E3 ubiquitin ligase best known for its ability to target protein degradation by the N-end rule. The physiological functions of UBR family proteins, however, remain not fully understood. We found that the functional loss of C. elegans UBR-1 leads to a specific Motor deficit: when adult animals generate reversal movements, A-class Motor neurons exhibit synchronized activation, preventing body bending. This Motor deficit is rescued by removing GOT-1, a transaminase that converts aspartate to glutamate. Both UBR-1 and GOT-1 are expressed and critically required in preMotor interneurons of the reversal Motor circuit to regulate the Motor Pattern. ubr-1 and got-1 mutants exhibit elevated and decreased glutamate level, respectively. These results raise an intriguing possibility that UBR proteins regulate glutamate metabolism, which is critical for neuronal development and signaling.
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the ubr 1 ubiquitin ligase regulates glutamate metabolism to generate coordinated Motor Pattern in c elegans
bioRxiv, 2018Co-Authors: Jythosna Chitturi, Wesley Hung, Anas Abdel M Rahman, Min Wu, John A Calarco, Renee Baran, Xun Huang, James W Dennis, Mei ZhenAbstract:UBR1 is an E3 ubiquitin ligase best known for its ability to target protein degradation by the N-end rule. The physiological functions of UBR family proteins, however, remain not fully understood. We found that the functional loss of C. elegans UBR-1 leads to a specific Motor deficit: when adult animals generate reversal movements, A-class Motor neurons exhibit synchronized activation, preventing body bending. This Motor deficit is rescued by removing GOT-1, a transaminase that converts aspartate to glutamate. Both UBR-1 and GOT-1 are expressed and critically required in preMotor interneurons of the reversal Motor circuit to regulate the Motor Pattern. ubr-1 and got-1 mutants exhibit elevated and decreased glutamate level, respectively. These results raise an intriguing possibility that UBR proteins regulate glutamate metabolism, which is critical for neuronal development and signaling.
Michael P Nusbaum - One of the best experts on this subject based on the ideXlab platform.
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divergent co transmitter actions underlie Motor Pattern activation by a modulatory projection neuron
European Journal of Neuroscience, 2007Co-Authors: Nicholas D Delong, Wolfgang Stein, Debra E Wood, Michael P NusbaumAbstract:Co-transmission is a common means of neuronal communication, but its consequences for neuronal signaling within a defined neuronal circuit remain unknown in most systems. We are addressing this issue in the crab stomatogastric nervous system by characterizing how the identified modulatory commissural neuron (MCN)1 uses its co-transmitters to activate the gastric mill (chewing) rhythm in the stomatogastric ganglion (STG). MCN1 contains gamma-aminobutyric acid (GABA) plus the peptides proctolin and Cancer borealis tachykinin-related peptide Ia (CabTRP Ia), which it co-releases during the retractor phase of the gastric mill rhythm to influence both retractor and protractor neurons. By focally applying each MCN1 co-transmitter and pharmacologically manipulating each co-transmitter action during MCN1 stimulation, we found that MCN1 has divergent co-transmitter actions on the gastric mill central Pattern generator (CPG), which includes the neurons lateral gastric (LG) and interneuron 1 (Int1), plus the STG terminals of MCN1 (MCN1(STG)). MCN1 used only CabTRP Ia to influence LG, while it used only GABA to influence Int1 and the contralateral MCN1(STG). These MCN1 actions caused a slow excitation of LG, a fast excitation of Int1 and a fast inhibition of MCN1(STG). MCN1-released proctolin had no direct influence on the gastric mill CPG, although it likely indirectly regulates this CPG via its influence on the pyloric rhythm. MCN1 appeared to have no ionotropic actions on the gastric mill follower Motor neurons, but it did use proctolin and/or CabTRP Ia to excite them. Thus, a modulatory projection neuron can elicit rhythmic Motor activity by using distinct co-transmitters, with different time courses of action, to simultaneously influence different CPG neurons.
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A small-systems approach to Motor Pattern generation.
Nature, 2002Co-Authors: Michael P Nusbaum, Mark P. BeenhakkerAbstract:How neuronal networks enable animals, humans included, to make coordinated movements is a continuing goal of neuroscience research. The stomatogastric nervous system of decapod crustaceans, which contains a set of distinct but interacting Motor circuits, has contributed significantly to the general principles guiding our present understanding of how rhythmic Motor circuits operate at the cellular level. This results from a detailed documentation of the circuit dynamics underlying Motor Pattern generation in this system as well as its modulation by individual transmitters and neurons.
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Distinct Functions for Cotransmitters Mediating Motor Pattern Selection
The Journal of neuroscience : the official journal of the Society for Neuroscience, 1999Co-Authors: Dawn M. Blitz, Michael P NusbaumAbstract:Motor Patterns are selected from multifunctional networks by selective activation of different projection neurons, many of which contain multiple transmitters. Little is known about how any individual projection neuron uses its cotransmitters to select a Motor Pattern. We address this issue by using the stomatogastric ganglion (STG) of the crab Cancer borealis, which contains a neuronal network that generates multiple versions of the pyloric and gastric mill Motor Patterns. The functional flexibility of this network results mainly from modulatory inputs it receives from projection neurons that originate in neighboring ganglia. We demonstrated previously that the STG Motor Pattern selected by activation of the modulatory proctolin neuron (MPN) results from direct MPN modulation of the pyloric rhythm and indirect MPN inhibition of the gastric mill rhythm. The latter action results from MPN inhibition of projection neurons that excite the gastric mill rhythm. These projection neurons are modulatory commissural neuron 1 (MCN1) and commissural projection neuron 2 (CPN2). MPN excitation of the pyloric rhythm is mimicked by bath application of proctolin, its peptide transmitter. Here, we show that MPN uses only its small molecule transmitter, GABA, to inhibit MCN1 and CPN2 within their ganglion of origin. We also demonstrate that MPN has no proctolin-mediated influence on MCN1 or CPN2, although exogenously applied proctolin directly excites these neurons. Thus, Motor Pattern selection occurs during MPN activation via proctolin actions on the STG network and GABA-mediated actions on projection neurons in the commissural ganglia, demonstrating a spatial and functional segregation of cotransmitter actions.
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intercircuit control of Motor Pattern modulation by presynaptic inhibition
The Journal of Neuroscience, 1997Co-Authors: Marlene Bartos, Michael P NusbaumAbstract:Rhythmically active neural networks can control the modulatory input that they receive via their synaptic effects onto modulatory neurons. This synaptic control of network modulation can occur presynaptically, at the axon terminals of the modulatory neuron. For example, in the crab stomatogastric ganglion (STG), a gastric mill network neuron presynaptically inhibits transmitter release from a modulatory projection neuron called modulatory commissural neuron 1. We showed previously that the gastric mill rhythm-timed presynaptic inhibition of the STG terminals of MCN1 is pivotal for enabling MCN1 to activate this rhythm. We also showed that MCN1 excites the pyloric rhythm within the STG. Here we show that, because MCN1 stimulation conjointly excites the gastric mill and pyloric rhythms, the gastric mill rhythm-timed presynaptic inhibition of MCN1 causes a rhythmic interruption in the MCN1-mediated excitation of the pyloric rhythm. Consequently, during each protraction phase of the gastric mill rhythm, presynaptic inhibition suppresses MCN1 excitation of the pyloric rhythm, thereby weakening the pyloric rhythm. During the retraction phase, presynaptic inhibition is absent and MCN1 elicits a faster, stronger, and modified pyloric rhythm. Thus, in addition to its role in enabling a neural circuit to regulate the modulatory transmission that it receives, presynaptic inhibition is also used effectively to rhythmically control the activity level of a distinct, but behaviorally related, neural circuit.
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cyclic nucleotide mediated modulation of the pyloric Motor Pattern in the stomatogastric ganglion of the crab cancer borealis
The Biological Bulletin, 1991Co-Authors: Nelson Spruston, Michael P NusbaumAbstract:The mechanisms responsible for controlling Patterned Motor behavior have been studied extensively in the stomatogastric ganglion (STG) of decapod crustaceans (1). This small ganglion of approximately 30 neurons generates the gastric mill and pyloric Motor Patterns, which underlie the chewing and subsequent movement of food from the stomach to the midgut, respectively. Despite its apparent simplicity, the STG generates many variations of both Motor Patterns, due to the influence of modulatory substances released in the STG neuropil from inputs to the ganglion. These modulatory inputs alter the frequency of the Motor Pattern, phase relationships and activity levels of individual STG neurons, and can even cause the switching of individual neurons between functionally distinct STG networks (2). The STG Motor Patterns are dependent upon the presence of these inputs, and they cease when the ganglion is isolated from its input. From this quiescent state, the pyloric rhythm can be induced by bath application of any of the known STG modulators. Although many modulators have been identified in the STG and their effects on the pyloric rhythm characterized, little is known about the second messenger systems that presumably mediate these effects. We have therefore begun to examine the role of cyclic adenosine monophosphate (CAMP) and cyclic guanosine monophosphate (cGMP) in modulating the pyloric rhythm in the STG of the crab,