Monoamines increase the excitability of spinal neurones in the neonatal rat by hyperpolarizing the threshold for action potential production

Fedirchuk, Brent; Dai, Yue

doi:10.1113/jphysiol.2004.064022

Cited by 89 publications

(65 citation statements)

References 30 publications

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“…Supporting a direct effect on the CINs, 5-HT modified the action potential properties in dCINs, decreasing the voltage threshold for action potential generation. This is in agreement with previous studies in rat motoneurons and unidentified ventral horn neurons, in which 5-HT reduces the threshold for the action potential generation, making neurons more excitable to synaptic inputs (Fedirchuk and Dai, 2004;Gilmore and Fedirchuk, 2004). We also showed that the amplitude of the postspike AHP is reduced in dCINs; this can contribute to neuronal excitability (Grillner, 2003).…”

Section: Different Modulation Of Dcins and Adcins By Serotoninsupporting

confidence: 81%

Intrinsic and Functional Differences among Commissural Interneurons during Fictive Locomotion and Serotonergic Modulation in the Neonatal Mouse

Zhong

Díaz‐Ríos

Harris-Warrick

2006

Journal of Neuroscience

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Commissural interneurons (CINs) send their axons across the midline to innervate contralateral targets and have been implicated in the coordination of left-right limb movements during locomotion. In the neonatal mouse spinal cord, we studied the firing properties and responses to serotonin (5-HT) of two classes of CINs: those whose axons turn caudally after crossing the midline (dCINs) and those whose axons bifurcate after crossing the midline (adCINs). During NMDA and 5-HT-induced locomotor-like activity, a majority of lumbar (L2) dCINs fired rhythmically with ventral root-recorded motor activity, although their firing phase was widely distributed throughout the locomotor cycle. In contrast, none of the adCINs fired rhythmically during fictive locomotion. We studied the baseline firing and membrane properties, and responses to current injection, in dCINs and adCINs that had been partially isolated by blockade of rapid synaptic transmission (with antagonists to glutamate, GABA, and glycine). No significant baseline differences were found between the cell types. In contrast, 5-HT significantly increased the excitability of the isolated dCINs by depolarizing the membrane potential, reducing the postspike afterhyperpolarization amplitude and decreasing the action potential threshold. None of these parameters were affected by 5-HT in adCINs. These results, together with our recent study of a third class of CINs, the aCINs whose axons ascend after crossing the midline (Zhong et al., 2006), suggest that dCINs and aCINs, but not adCINs, are excited by 5-HT and are rhythmically active during fictive locomotion. Thus, they may play important roles in the coordination of left-right movements during fictive locomotion.

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Section: Different Modulation Of Dcins and Adcins By Serotoninsupporting

confidence: 81%

Intrinsic and Functional Differences among Commissural Interneurons during Fictive Locomotion and Serotonergic Modulation in the Neonatal Mouse

Zhong

Díaz‐Ríos

Harris-Warrick

2006

Journal of Neuroscience

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“…It has been previously reported that DA causes a statistically significant increase in the peak amplitude of the PIR in DE-3, but not the area under the curve (Vallecorsa et al, 2007). An increase in overall cellular excitability is one way that neuromodulators can exert their influence over CPG activation (Clemens and Katz, 2003;Dai et al, 1998;Fedirchuk and Dai, 2004;Katz, 1998;Katz and Frost, 1997). Based on firing frequency, as an indicator of cell excitability, we found that DA reduced neuronal excitability, but only in the context of current injection.…”

Section: Pdis and Da Exert Distinct Effects On Specific Crawl-relatedmentioning

confidence: 93%

Mechanisms contributing to the dopamine induction of crawl-like bursting in leech motoneurons

Crisp

Gallagher

Mesce

2012

Journal of Experimental Biology

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SUMMARY Dopamine (DA) activates fictive crawling behavior in the medicinal leech. To identify the cellular mechanisms underlying this activation at the level of crawl-specific motoneuronal bursting, we targeted potential cAMP-dependent events that are often activated through DA 1 -like receptor signaling pathways. We found that isolated ganglia produced crawl-like motoneuron bursting after bath application of phosphodiesterase inhibitors (PDIs) that upregulated cAMP. This bursting persisted in salines in which calcium ions were replaced with equimolar cobalt or nickel, but was blocked by riluzole, an inhibitor of a persistent sodium current. PDI-induced bursting contained a number of patterned elements that were statistically similar to those observed during DA-induced fictive crawling, except that one motoneuron (CV) exhibited bursting during the contraction rather than the elongation phase of crawling. Although DA and the PDIs produced similar bursting profiles, intracellular recordings from motoneurons revealed differences in altered membrane properties. For example, DA lowered motoneuron excitability whereas the PDIs increased resting discharge rates. We suggest that PDIs (and DA) activate a sodium-influx-dependent timing mechanism capable of setting the crawl rhythm and that multiple DA receptor subtypes are involved in shaping and modulating the phase relationships and membrane properties of cell-specific members of the crawl network to generate crawling.

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“…Serotonergic agonists hyperpolarize the action potential threshold (Wikstrom et al, 1995;Grillner et al, 2001;Hill et al, 2003) and shorten the duration of afterhyperpolarization (Fedirchuk and Dai, 2004). These changes frequently bring the membrane potentials of spinal neurons near the threshold required to generate plateau potentials, which have been hypothesized to be the basis for locomotor drive potentials.…”

Section: Discussionmentioning

confidence: 99%

Spinal Cord-Transected Mice Learn to Step in Response to Quipazine Treatment and Robotic Training

Fong¹,

Cai²,

Otoshi³

et al. 2005

J. Neurosci.

128

126

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In the present study, concurrent treatment with robotic step training and a serotonin agonist, quipazine, generated significant recovery of locomotor function in complete spinal cord-transected mice (T7-T9) that otherwise could not step. The extent of recovery achieved when these treatments were combined exceeded that obtained when either treatment was applied independently. We quantitatively analyzed the stepping characteristics of spinal mice after alternatively administering no training, manual training, robotic training, quipazine treatment, or a combination of robotic training with quipazine treatment, to examine the mechanisms by which training and quipazine treatment promote functional recovery. Using fast Fourier transform and principal components analysis, significant improvements in the step rhythm, step shape consistency, and number of weight-bearing steps were observed in robotically trained compared with manually trained or nontrained mice. In contrast, manual training had no effect on stepping performance, yielding no improvement compared with nontrained mice. Daily bolus quipazine treatment acutely improved the step shape consistency and number of steps executed by both robotically trained and nontrained mice, but these improvements did not persist after quipazine was withdrawn. At the dosage used (0.5 mg/kg body weight), quipazine appeared to facilitate, rather than directly generate, stepping, by enabling the spinal cord neural circuitry to process specific patterns of sensory information associated with weight-bearing stepping. Via this mechanism, quipazine treatment enhanced kinematically appropriate robotic training. When administered intermittently during an extended period of robotic training, quipazine revealed training-induced stepping improvements that were masked in the absence of the pharmacological treatment.

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Monoamines increase the excitability of spinal neurones in the neonatal rat by hyperpolarizing the threshold for action potential production

Cited by 89 publications

References 30 publications

Intrinsic and Functional Differences among Commissural Interneurons during Fictive Locomotion and Serotonergic Modulation in the Neonatal Mouse

Intrinsic and Functional Differences among Commissural Interneurons during Fictive Locomotion and Serotonergic Modulation in the Neonatal Mouse

Mechanisms contributing to the dopamine induction of crawl-like bursting in leech motoneurons

Spinal Cord-Transected Mice Learn to Step in Response to Quipazine Treatment and Robotic Training

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