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TTX-resistant NMDA receptor-mediated membrane potential oscillations in neonatal mouse Hb9 interneurons.

Masino MA, Abbinanti MD, Eian J, Harris-Warrick RM - PLoS ONE (2012)

Bottom Line: Hb9 interneurons are rhythmically active during fictive locomotor-like behavior.In contrast, exogenous serotonin and dopamine application, alone or in combination, are not sufficient.NMDA does not modulate the T-type calcium current (I(Ca(T))), which is thought to be important in generating locomotor-like activity, in Hb9 neurons.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States of America. masino@umn.edu

ABSTRACT
Conditional neuronal membrane potential oscillations have been identified as a potential mechanism to help support or generate rhythmogenesis in neural circuits. A genetically identified population of ventromedial interneurons, called Hb9, in the mouse spinal cord has been shown to generate TTX-resistant membrane potential oscillations in the presence of NMDA, serotonin and dopamine, but these oscillatory properties are not well characterized. Hb9 interneurons are rhythmically active during fictive locomotor-like behavior. In this study, we report that exogenous N-Methyl-D-Aspartic acid (NMDA) application is sufficient to produce membrane potential oscillations in Hb9 interneurons. In contrast, exogenous serotonin and dopamine application, alone or in combination, are not sufficient. The properties of NMDA-induced oscillations vary among the Hb9 interneuron population; their frequency and amplitude increase with increasing NMDA concentration. NMDA does not modulate the T-type calcium current (I(Ca(T))), which is thought to be important in generating locomotor-like activity, in Hb9 neurons. These results suggest that NMDA receptor activation is sufficient for the generation of TTX-resistant NMDA-induced membrane potential oscillations in Hb9 interneurons.

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Concentration dependence of NMDA-induced membrane potential oscillations in Hb9 interneurons. A,Whole-cell current-clamp recordings of membrane potential from a single Hb9 interneuron at several NMDA concentrations. Note the lowest NMDA concentration (6 μM) does not induce oscillations. B–C, NMDA dose-response curves for cycle frequency show a linear relation above 6 μM (r = 0.87, p<0.001, n = 20) and voltage amplitude (r = 0.92, p<0.001, n = 20). The threshold for oscillation activation is ∼9 μM. Data are normalized to 15 μM.
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pone-0047940-g003: Concentration dependence of NMDA-induced membrane potential oscillations in Hb9 interneurons. A,Whole-cell current-clamp recordings of membrane potential from a single Hb9 interneuron at several NMDA concentrations. Note the lowest NMDA concentration (6 μM) does not induce oscillations. B–C, NMDA dose-response curves for cycle frequency show a linear relation above 6 μM (r = 0.87, p<0.001, n = 20) and voltage amplitude (r = 0.92, p<0.001, n = 20). The threshold for oscillation activation is ∼9 μM. Data are normalized to 15 μM.

Mentions: To determine the NMDA concentration dependence of the Hb9 interneuron oscillations, we applied a series of NMDA concentrations (3 to 21 μM) to transverse slice preparations in the presence of TTX and monitored the Hb9 membrane potential. Lower NMDA concentrations (3 or 6 μM) did not generate membrane potential oscillations in these cells (0 of 4; Fig. 3A, top trace). Membrane potential oscillations were generated between 9 and 21 μM NMDA; the lowest effective NMDA concentration that elicited oscillations was 9 μM (3 of 4; Fig. 3B & C).


TTX-resistant NMDA receptor-mediated membrane potential oscillations in neonatal mouse Hb9 interneurons.

Masino MA, Abbinanti MD, Eian J, Harris-Warrick RM - PLoS ONE (2012)

Concentration dependence of NMDA-induced membrane potential oscillations in Hb9 interneurons. A,Whole-cell current-clamp recordings of membrane potential from a single Hb9 interneuron at several NMDA concentrations. Note the lowest NMDA concentration (6 μM) does not induce oscillations. B–C, NMDA dose-response curves for cycle frequency show a linear relation above 6 μM (r = 0.87, p<0.001, n = 20) and voltage amplitude (r = 0.92, p<0.001, n = 20). The threshold for oscillation activation is ∼9 μM. Data are normalized to 15 μM.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3475713&req=5

pone-0047940-g003: Concentration dependence of NMDA-induced membrane potential oscillations in Hb9 interneurons. A,Whole-cell current-clamp recordings of membrane potential from a single Hb9 interneuron at several NMDA concentrations. Note the lowest NMDA concentration (6 μM) does not induce oscillations. B–C, NMDA dose-response curves for cycle frequency show a linear relation above 6 μM (r = 0.87, p<0.001, n = 20) and voltage amplitude (r = 0.92, p<0.001, n = 20). The threshold for oscillation activation is ∼9 μM. Data are normalized to 15 μM.
Mentions: To determine the NMDA concentration dependence of the Hb9 interneuron oscillations, we applied a series of NMDA concentrations (3 to 21 μM) to transverse slice preparations in the presence of TTX and monitored the Hb9 membrane potential. Lower NMDA concentrations (3 or 6 μM) did not generate membrane potential oscillations in these cells (0 of 4; Fig. 3A, top trace). Membrane potential oscillations were generated between 9 and 21 μM NMDA; the lowest effective NMDA concentration that elicited oscillations was 9 μM (3 of 4; Fig. 3B & C).

Bottom Line: Hb9 interneurons are rhythmically active during fictive locomotor-like behavior.In contrast, exogenous serotonin and dopamine application, alone or in combination, are not sufficient.NMDA does not modulate the T-type calcium current (I(Ca(T))), which is thought to be important in generating locomotor-like activity, in Hb9 neurons.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States of America. masino@umn.edu

ABSTRACT
Conditional neuronal membrane potential oscillations have been identified as a potential mechanism to help support or generate rhythmogenesis in neural circuits. A genetically identified population of ventromedial interneurons, called Hb9, in the mouse spinal cord has been shown to generate TTX-resistant membrane potential oscillations in the presence of NMDA, serotonin and dopamine, but these oscillatory properties are not well characterized. Hb9 interneurons are rhythmically active during fictive locomotor-like behavior. In this study, we report that exogenous N-Methyl-D-Aspartic acid (NMDA) application is sufficient to produce membrane potential oscillations in Hb9 interneurons. In contrast, exogenous serotonin and dopamine application, alone or in combination, are not sufficient. The properties of NMDA-induced oscillations vary among the Hb9 interneuron population; their frequency and amplitude increase with increasing NMDA concentration. NMDA does not modulate the T-type calcium current (I(Ca(T))), which is thought to be important in generating locomotor-like activity, in Hb9 neurons. These results suggest that NMDA receptor activation is sufficient for the generation of TTX-resistant NMDA-induced membrane potential oscillations in Hb9 interneurons.

Show MeSH
Related in: MedlinePlus