A Slow Outward Current Activated by FMRFamide in Heart Interneurons of the Medicinal Leech

Nadim, Farzan; Calabrese, Ronald L.

doi:10.1523/jneurosci.17-11-04461.1997

Cited by 29 publications

(21 citation statements)

References 35 publications

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“…I Proc is modeled by Equation (18), while the slow current (I K ) is modeled by Equation (20). Physiologically, I K is similar to the slow, noninactivating, K + current (I KF ) found in the heartbeat CPG of the medicinal leech (Nadim and Calabrese, 1997).…”

Section: Pk Induction Of I Proc + I K In the Lg Neuron Elicits An Mcnsupporting

confidence: 55%

A modeling comparison of projection neuron- and neuromodulator-elicited oscillations in a central pattern generating network

2007

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Many central pattern generating networks are influenced by synaptic input from modulatory projection neurons. The network response to a projection neuron is sometimes mimicked by bath applying the neuronally-released modulator, despite the absence of network interactions with the projection neuron. One interesting example occurs in the crab stomatogastric ganglion (STG), where bath applying the neuropeptide pyrokinin (PK) elicits a gastric mill rhythm which is similar to that elicited by the projection neuron MCN1, despite the absence of PK in MCN1 and the fact that MCN1 is not active during the PK-elicited rhythm. MCN1 terminals have fast and slow synaptic actions on the gastric mill network and are presynaptically inhibited by this network in the STG. These local connections are inactive in the PK-elicited rhythm, and the mechanism underlying this rhythm is unknown. We use mathematical and biophysically-realistic modeling to propose potential mechanisms by which PK can elicit a gastric mill rhythm that is similar to the MCN1-elicited rhythm. We analyze slow-wave network oscillations using simplified mathematical models and, in parallel, develop biophysically-realistic models that account for fast, action potential-driven oscillations and some spatial structure of the network neurons. Our results illustrate how the actions of bath-applied neuromodulators can mimic those of descending projection neurons through mathematically similar but physiologically distinct mechanisms.

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Section: Pk Induction Of I Proc + I K In the Lg Neuron Elicits An Mcnsupporting

confidence: 55%

A modeling comparison of projection neuron- and neuromodulator-elicited oscillations in a central pattern generating network

2007

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“…Both the effect of FMRFa and the effect on the heart following HE stimulation are long lasting. Calabrese et al (1995) and Nadim and Calabrese 1997) consider that the primary excitatory effect of FMRFa on the leech heart is through activation of a slow outward potassium current (I KF ) in heart interneurones, and these currents have very slow activation and deactivation kinetics. FMRFa also excites the longitudinal muscle of the leech Calabrese 1987, 1990).…”

Section: Annelidsmentioning

confidence: 99%

A review of FMRFamide- and RFamide-like peptides in metazoa

2009

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Neuropeptides are a diverse class of signalling molecules that are widely employed as neurotransmitters and neuromodulators in animals, both invertebrate and vertebrate. However, despite their fundamental importance to animal physiology and behaviour, they are much less well understood than the small molecule neurotransmitters. The neuropeptides are classified into families according to similarities in their peptide sequence; and on this basis, the FMRFamide and RFamide-like peptides, first discovered in molluscs, are an example of a family that is conserved throughout the animal phyla. In this review, the literature on these neuropeptides has been consolidated with a particular emphasis on allowing a comparison between data sets in phyla as diverse as coelenterates and mammals. The intention is that this focus on the structure and functional aspects of FMRFamide and RFamide-like neuropeptides will inform understanding of conserved principles and distinct properties of signalling across the animal phyla.

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“…Extensive electrophysiological characterization of the ionic conductances in the oscillator interneurons has led to the development of a conductance-based single-compartment model of the oscillator interneurons ). An earlier generation of this model (Nadim et al 1995) guided experiments investigating which conductances are targeted by the endogenous leech peptide FMRFamide to accelerate the rhythmic bursting of the oscillator heart interneurons (Nadim and Calabrese 1997).…”

Section: Introductionmentioning

confidence: 99%

Endogenous and Half-Center Bursting in Morphologically Inspired Models of Leech Heart Interneurons

Tobin

Calabrese²

2006

Journal of Neurophysiology

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Based on a detailed morphology 'Full Model' of a leech heart interneuron, we previously developed a computationally-efficient, morphologically-inspired 'Reduced Model' to expedite tuning the model to produce endogenous bursting and alternating bursting when configured as a half-center oscillator (paired with reciprocally inhibitory synapses). To find conductance density distributions that produce endogenous bursting, we implemented a genetic algorithm automated parameter search. With multiple searches, we found eight parameter sets that produced endogenous bursting in the Reduced Model. When these parameter sets were applied to the Full Model, all produced endogenous bursting, although when the simulation time was extended from 80 s to 300 s, only four parameter sets produced sustained bursting in the Reduced Models. All parameter sets produced alternating half-center bursting in the Reduced and Full Models throughout 300 s. When conductance amplitudes were systematically varied for each of the four sustained burster sets, the effects on bursting activity differed, both for the same parameter set in the Reduced and Full Models and for different parameter sets with the same level of morphological detail. This implies that morphological detail can affect burst activity and that these parameter sets may represent different mechanisms for burst generation and/or regulation. We also tested the models with parameter variations that correspond to experimental manipulations. We conclude that whereas similar output can be achieved with multiple different parameter sets, perturbations such as conductance variations can highlight differences. Additionally, this work demonstrates both the utility and limitations of using simplified models to represent more morphologically-accurate models.

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A Slow Outward Current Activated by FMRFamide in Heart Interneurons of the Medicinal Leech

Cited by 29 publications

References 35 publications

A modeling comparison of projection neuron- and neuromodulator-elicited oscillations in a central pattern generating network

A modeling comparison of projection neuron- and neuromodulator-elicited oscillations in a central pattern generating network

A review of FMRFamide- and RFamide-like peptides in metazoa

Endogenous and Half-Center Bursting in Morphologically Inspired Models of Leech Heart Interneurons

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