Description: Neuromodulation is well known to provide plasticity in pattern generating circuits, but few details are available concerning modulation of motor pattern coordination. We are using the crustacean stomatogastric nervous system to examine how co-expressed rhythms are modulated to regulate frequency and maintain coordination. The system produces two related motor patterns, the gastric mill rhythm that regulates protraction and retraction of the teeth and the pyloric rhythm that filters food. These rhythms have different frequencies and are controlled by distinct mechanisms, but each circuit influences the rhythm frequency of the other via identified synaptic pathways. A projection neuron, MCN1, activates distinct versions of the rhythms, and we show that hormonal dopamine concentrations modulate the MCN1 elicited rhythm frequencies. Gastric mill circuit interactions with the pyloric circuit lead to changes in pyloric rhythm frequency that depend on gastric mill rhythm phase. Dopamine increases pyloric frequency d
Authors: Wood, DE;Varrecchia, M;Papernov, M;Cook, D;Crawford, DC
Source: Journal of neurophysiology; 104, 2, 654-64; 2010 Aug
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Description: Postsynaptic release of Ca2+ from intracellular stores is an important means of cellular signaling that mediates numerous forms of synaptic plasticity. Previous studies have identified a postsynaptic intracellular Ca2+ requirement for a form of short-term plasticity, post-tetanic potentiation (PTP) at sensory neuron (SN)–motor neuron synapses in Aplysia. Here, we show that postsynaptic IP3-mediated Ca2+ release in response to a presynaptic tetanus in an SN that induces PTP can confer transient plasticity onto a neighboring SN synapse receiving subthreshold activation. This heterosynaptic sharing of plasticity represents a dynamic, short-term synaptic enhancement of synaptic inputs onto a common postsynaptic target. Heterosynaptic sharing is blocked by postsynaptic disruption of Ca2+- and IP3-mediated signaling, and, conversely, it is mimicked by postsynaptic injection of nonhydrolyzable IP3, and by photolysis of caged IP3 in the MN. The molecular mechanism for heterosynaptic sharing involves metabotropic glut
Tags: Aplysia, PTP, caged calcium
Authors: Reissner, KJ;Pu, L;Schaffhausen, JH;Boyle, HD;Smith, IF;Parker, I;Carew, TJ
Source: The Journal of neuroscience : the official journal of the Society for Neuroscience; 30, 26, 8797-806; 2010 Jun 30
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Authors: Crocker, A;Shahidullah, M;Levitan, IB;Sehgal, A
Source: Neuron; 65, 5, 670-81; 2010 Mar 11
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Authors: Lee, MC;Yasuda, R;Ehlers, MD
Source: Neuron; 66, 6, 859-70; 2010 Jun 24
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Authors: Christie, AE;Stemmler, EA;Dickinson, PS
Source: Cellular and molecular life sciences : CMLS; 2010 Aug 21; 2010 Aug 21
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Description: Aplysia californica is a powerful experimental system to study the entire scope of genomic and epigenomic regulation at the resolution of single functionally characterized neurons and is an emerging model in the neurobiology of aging. First, we have identified and cloned a number of evolutionarily conserved genes that are age-related, including components of apoptosis and chromatin remodeling. Second, we performed gene expression profiling of different identified cholinergic neurons between young and aged animals. Our initial analysis indicates that two cholinergic neurons (R2 and LPl1) revealed highly differential genome-wide changes following aging suggesting that on the molecular scale different neurons indeed age differently. Each of the neurons tested has a unique subset of genes differentially expressed in older animals, and the majority of differently expressed genes (including those related to apoptosis and Alzheimer's disease) are found in aging neurons of one but not another type. The performed anal
Tags: Aplysia, aging, genes
Authors: Moroz, LL;Kohn, AB
Source: Frontiers in aging neuroscience; 2; 2010 May 19
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Description: How can flexible phasing be generated by a central pattern generator (CPG)? To address this question, we have extended an existing model of the leech heartbeat CPG's timing network to construct a model of the CPG core and explore how appropriate phasing is set up by parameter variation. Within the CPG, the phasing among premotor interneurons switches regularly between two well defined states - synchronous and peristaltic. To reproduce experimentally observed phasing, we varied the strength of inhibitory synaptic and excitatory electrical input from the timing network to follower premotor interneurons. Neither inhibitory nor electrical input alone was sufficient to produce proper phasing on both sides, but instead a balance was required. Our model suggests that the different phasing of the two sides arises because the inhibitory synapses and electrical coupling oppose one another on one side (peristaltic) and reinforce one another on the other (synchronous). Our search of parameter space defined by the strengt
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Description: The output of a neural circuit results from an interaction between the intrinsic properties of neurons in the circuit and the features of the synaptic connections between them. The plasticity of intrinsic properties has been primarily attributed to modification of ion channel function and/or number. We have found a mechanism for intrinsic plasticity in rhythmically active Drosophila neurons that was not based on changes in ion conductance. Larval motor neurons had a long-lasting, sodium-dependent afterhyperpolarization (AHP) following bursts of action potentials that was mediated by the electrogenic activity of Na(+)/K(+) ATPase. This AHP persisted for multiple seconds following volleys of action potentials and was able to function as a pattern-insensitive integrator of spike number that was independent of external calcium. This current also interacted with endogenous Shal K(+) conductances to modulate spike timing for multiple seconds following rhythmic activity, providing a cellular memory of network activi
Authors: Pulver, SR;Griffith, LC
Source: Nature neuroscience; 13, 1, 53-9; 2010 Jan
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Description: Recent theoretical and experimental work indicates that neurons tune themselves to maintain target levels of excitation by modulating ion channel expression and synaptic strengths. As a result, functionally equivalent circuits can produce similar activ...
Tags: intrinsic conductances, dynamic clamp, synaptic
Authors: Grashow, Rachel ; Brookings, Ted ; Marder, Eve
Source: The Journal of neuroscience : the official journal of the Society for Neuroscience; 30, 27, 9145 9156 12
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Description: Mollusks are a showcase of brain evolution represented by several classes with a varying degree of nervous system centralization. Cellular and molecular processes involved in the evolution of the highly complex cephalopod brain from a simple, monoplacophoran-like ancestor are still obscure and homologies on the cellular level are poorly established. FMRFamide (Phe-Ile-Arg-Phe-NH(2))-related peptides (FaRPs) constitute an evolutionarily conserved and diverse group of neuropeptides in the central nervous system (CNS) of many metazoans. Herein, we provide a detailed description of the developing FMRFamide-like immunoreactive (Fa-lir) CNS of the pygmy squid Idiosepius notoides using gene expression analyses and immunocytochemistry. The open reading frame of the I. notoides FMRFamide gene InFMRF predicts one copy each of FIRFamide, FLRFamide (Phe-Leu-Arg-Phe-NH(2)), ALSGDAFLRFamide (Ala-Leu-Ser-Gly-Asp-Ala-Phe-Leu-Arg-Phe-NH(2)), and 11 copies of FMRFamide. Applying matrix-assisted laser desorption/ionization time
Tags: FRMFamide, evolution, cephalopod
Authors: Wollesen, T;Cummins, SF;Degnan, BM;Wanninger, A
Source: Evolution & development; 12, 2, 113-30; 2010 Mar
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Description: Calmodulin (CaM)-sensitive adenylyl cyclase (AC) in sensory neurons (SNs) in Aplysia has been proposed as a molecular coincidence detector during conditioning. We identified four putative ACs in Aplysia CNS. CaM binds to a sequence in the C1b region of AC-AplA that resembles the CaM-binding sequence in the C1b region of AC1 in mammals. Recombinant AC-AplA was stimulated by Ca(2+)/CaM. AC-AplC is most similar to the Ca(2+)-inhibited AC5 and AC6 in mammals. Recombinant AC-AplC was directly inhibited by Ca(2+), independent of CaM. AC-AplA and AC-AplC are expressed in SNs, whereas AC-AplB and AC-AplD are not. Knockdown of AC-AplA demonstrated that serotonin stimulation of cAMP-dependent plasticity in SNs is predominantly mediated by this CaM-sensitive AC. We propose that the coexpression of a Ca(2+)-inhibited AC in SNs, together with a Ca(2+)/CaM-stimulated AC, would enhance the associative requirement for coincident Ca(2+) influx and serotonin for effective stimulation of cAMP levels and initiation of plasticity
Tags: Aplysia, calcium, cAMP
Authors: Lin, AH;Cohen, JE;Wan, Q;Niu, K;Shrestha, P;Bernstein, SL;Abrams, TW
Source: Proceedings of the National Academy of Sciences of the United States of America; 2010 Aug 11
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Description: The detection of odour stimuli in the environment is universally important for primal behaviours such as feeding, mating, kin interactions and escape responses. Given the ubiquity of many airborne chemical signals and the similar organisation of animal olfactory circuits, a fundamental question in our understanding of the sense of smell is how species-specific behavioural responses to odorants can evolve. Recent comparative genomic, developmental and physiological studies are shedding light on this problem by providing insights into the genetic mechanisms that underlie anatomical and functional evolution of the olfactory system. Here we synthesise these data, with a particular focus on insect olfaction, to address how new olfactory receptors and circuits might arise and diverge, offering glimpses into how odour-evoked behaviours could adapt to an ever-changing chemosensory world
Tags: evolution, olfaction, fly
Authors: Ramdya, P;Benton, R
Source: Trends in genetics : TIG; 26, 7, 307-16; 2010 Jul
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Description: The pteropod mollusk, Clione limacina, exhibits behaviorally relevant swim speed changes that occur within the context of the animal's ecology. Modulation of C. limacina swimming speed involves changes that occur at the network and cellular levels. Intracellular recordings from interneurons of the swim central pattern generator show the presence of a sag potential that is indicative of the hyperpolarization-activated inward current (I(h)). Here we provide evidence that I(h) in primary swim interneurons plays a role in C. limacina swimming speed control and may be a modulatory target. Recordings from central pattern generator swim interneurons show that hyperpolarizing current injection produces a sag potential that lasts for the duration of the hyperpolarization, a characteristic of cells possessing I(h). Following the hyperpolarizing current injection, swim interneurons also exhibit postinhibitory rebound (PIR). Serotonin enhances the sag potential of C. limacina swim interneurons while the I(h) blocker, ZD7
Tags: clione, swimming, Ih
Authors: Pirtle, TJ;Willingham, K;Satterlie, RA
Source: Comparative biochemistry and physiology. Part A, Molecular & integrative physiology; 2010 Aug 6
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Description: An animal's response to a stimulus depends on many factors such as age, hormonal state, experience, and its behavioral state. For example, an animal may suppress a behavior that is inappropriate or incompatible with its current state. In this study, we show that, as a medicinal leech feeds, the distention that it incurs inhibits its expression of swimming. Distention slows the swimming pattern and decreases the number of swim cycles elicited by a test electrical stimulation; large distentions inhibit swimming altogether. We have previously shown that the ingestive phase of feeding inhibits behaviors by presynaptic inhibition of mechanosensory neurons. Distention has its effects downstream (e.g., gating and central pattern generating interneurons) from these sensory neurons and thus represents a novel mechanism for choosing between conflicting behaviors during feeding. Because removing the leech's gut surgically did not eliminate the effects of body distention, we conclude that the receptors mediating the dist
Tags: leech, swimming, feeding
Source: The Journal of Neuroscience, July 21, 2010, 30(29):9753-9761
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Description: Postsynaptic release of Ca(2+) from intracellular stores is an important means of cellular signaling that mediates numerous forms of synaptic plasticity. Previous studies have identified a postsynaptic intracellular Ca(2+) requirement for a form of short-term plasticity, post-tetanic potentiation (PTP) at sensory neuron (SN)-motor neuron synapses in Aplysia. Here, we show that postsynaptic IP(3)-mediated Ca(2+) release in response to a presynaptic tetanus in an SN that induces PTP can confer transient plasticity onto a neighboring SN synapse receiving subthreshold activation. This heterosynaptic sharing of plasticity represents a dynamic, short-term synaptic enhancement of synaptic inputs onto a common postsynaptic target. Heterosynaptic sharing is blocked by postsynaptic disruption of Ca(2+)- and IP(3)-mediated signaling, and, conversely, it is mimicked by postsynaptic injection of nonhydrolyzable IP(3), and by photolysis of caged IP(3) in the MN. The molecular mechanism for heterosynaptic sharing involves m
Tags: Aplysia, ptp, plasticity
Authors: Reissner, KJ;Pu, L;Schaffhausen, JH;Boyle, HD;Smith, IF;Parker, I;Carew, TJ
Source: The Journal of neuroscience : the official journal of the Society for Neuroscience; 30, 26, 8797-806; 2010 Jun 30
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Description: Recent theoretical and experimental work indicates that neurons tune themselves to maintain target levels of excitation by modulating ion channel expression and synaptic strengths. As a result, functionally equivalent circuits can produce similar activity despite disparate underlying network and cellular properties. To experimentally test the extent to which synaptic and intrinsic conductances can produce target activity in the presence of variability in neuronal intrinsic properties, we used the dynamic clamp to create hybrid two-cell circuits built from four types of stomatogastric neurons coupled to the same model Morris–Lecar neuron by reciprocal inhibition. We measured six intrinsic properties (input resistance, minimum membrane potential, firing rate in response to +1 nA of injected current, slope of the frequency–current curve, spike height, and spike voltage threshold) of dorsal gastric, gastric mill, lateral pyloric, and pyloric dilator neurons from male crabs of the species Cancer borealis. The intr
Authors: Grashow, R;Brookings, T;Marder, E
Source: The Journal of neuroscience : the official journal of the Society for Neuroscience; 30, 27, 9145-56; 2010 Jul 7
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Description: There are now a reasonable number of invertebrate central pattern generator (CPG) circuits described in sufficient detail that a mechanistic explanation of how they work is possible. These small circuits represent the best-understood neural circuits with which to investigate how cell-to-cell synaptic connections and individual channel conductances combine to generate rhythmic and patterned output. In this review, some of the main lessons that have appeared from this analysis are discussed and concrete examples of circuits ranging from single phase to multiple phase patterns are described. While it is clear that the cellular components of any CPG are basically the same, the topology of the circuits have evolved independently to meet the particular motor requirements of each individual organism and only a few general principles of circuit operation have emerged. The principal usefulness of small systems in relation to the brain is to demonstrate in detail how cellular infrastructure can be used to generate rhyt
Tags: CPG, invertebrates
Authors: Selverston, AI
Source: Philosophical transactions of the Royal Society of London. Series B, Biological sciences; 365, 1551, 2329-45; 2010 Aug 12
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Description: The characteristics of central pattern generator (CPG) outputs are subject to extensive modulation. Previous studies of neuromodulation largely focused on immediate actions of neuromodulators, i.e., actions that were exerted at the time when either neuromodulators were present or neuromodulatory inputs to the CPG were active. However, neuromodulatory actions are known to persist when neuromodulators are no longer present. In Aplysia, stimulation of cerebral-buccal interneuron-2 (CBI-2), which activates the feeding CPG, produces a repetition priming of motor programs. This priming is reflected in an increase of firing of motoneurons. As CBI-2 contains two neuromodulatory peptides, FCAP (feeding circuit-activating peptide) and CP2 (cerebral peptide 2), we hypothesized that repetition priming may involve persistent peptidergic neuromodulation. We find that these peptides produce priming-like effects, i.e., they increase the firing of radula-opening (B48) and radula-closing (B8) motoneurons during motor programs.
Tags: Aplysia, cAMP
Authors: Friedman, AK;Weiss, KR
Source: The Journal of neuroscience : the official journal of the Society for Neuroscience; 30, 26, 8906-19; 2010 Jun 30
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Description: The buccal ganglia of the mollusc, Lymnaea stagnalis, contain two distinct but interacting rhythm-generating units: the central pattern generator for the buccal rhythm and nitrergic B2 neurons controlling gut motility. Nitric oxide (NO) has previously been demonstrated to be involved in the activation of the buccal rhythm. Here, we found that NO-generating substances (SNP and SNAP) activated the buccal rhythm while slowing the endogenous rhythm of B2 bursters. The inhibitor of NO-synthase, L-NNA, the NO scavenger PTIO, or the inhibitor of soluble guanylyl cyclase, ODQ, each produced opposite, depolarising effects on the B2 neuron. In isolated B2 cells, only depolarising effects of substances interfering with NO production or function (PTIO, L-NNA and ODQ) were detected, whereas the NO donors had no hyperpolarising effects. However, when an isolated B2 cell was placed close to its initial position in the ganglion, hyperpolarising effects could be obtained with NO donors. This indicates that extrasynaptic relea
Tags: Lymnaea stagnalis, NO
Authors: Dyakonova, VE;Dyakonova, TL
Source: Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology; 2010 Jun 18
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