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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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Distribution of cycle frequency and voltage amplitude for NMDA-induced membrane potential oscillations in Hb9 interneurons. A–B,Whole-cell current-clamp recordings of membrane potential from different Hb9 interneurons demonstrate variability of voltage amplitudes in NMDA induced oscillations. C1–3, Distribution plots of cycle frequency, voltage amplitude and burst strength. D1–3, There is no correlation between voltage amplitude and cycle frequency (D1; r = −0.10, p = 0.55, n = 40). However, correlations are found between burst strength and cycle frequency (D2; r = −0.39, p = 0.01, n = 40) and burst strength and voltage amplitude (D3; r = 0.92, p<0.001, n = 40).
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pone-0047940-g002: Distribution of cycle frequency and voltage amplitude for NMDA-induced membrane potential oscillations in Hb9 interneurons. A–B,Whole-cell current-clamp recordings of membrane potential from different Hb9 interneurons demonstrate variability of voltage amplitudes in NMDA induced oscillations. C1–3, Distribution plots of cycle frequency, voltage amplitude and burst strength. D1–3, There is no correlation between voltage amplitude and cycle frequency (D1; r = −0.10, p = 0.55, n = 40). However, correlations are found between burst strength and cycle frequency (D2; r = −0.39, p = 0.01, n = 40) and burst strength and voltage amplitude (D3; r = 0.92, p<0.001, n = 40).

Mentions: The properties of the TTX-resistant NMDA-induced oscillations were variable between Hb9 interneurons (Fig. 2A & B). To quantify this variability, we measured cycle frequency, voltage amplitude and burst strength from a common trough potential, held at −60 mV with bias current. The cycle frequency of NMDA-induced oscillations ranged from 0.34 to 0.95 Hz (mean  = 0.61±0.15 Hz, n = 40; Fig. 2C1). The voltage amplitude of NMDA induced oscillations ranged from 1.9 to 41.2 mV (mean  = 12.8±9.5 mV, n = 40; Fig. 2C2) with 70% (28 of 40) less than 15 mV. The burst strength of NMDA-induced oscillations ranged from 0.9 to 25.3 mV*sec (mean  = 7.2±5.9 mV*sec, n = 40; Fig. 2C3) with 75% (30 of 40) less than 10 mV*sec. These values do not show a bimodal distribution, suggesting that they reflect variation of a single population of Hb9 neurons.


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)

Distribution of cycle frequency and voltage amplitude for NMDA-induced membrane potential oscillations in Hb9 interneurons. A–B,Whole-cell current-clamp recordings of membrane potential from different Hb9 interneurons demonstrate variability of voltage amplitudes in NMDA induced oscillations. C1–3, Distribution plots of cycle frequency, voltage amplitude and burst strength. D1–3, There is no correlation between voltage amplitude and cycle frequency (D1; r = −0.10, p = 0.55, n = 40). However, correlations are found between burst strength and cycle frequency (D2; r = −0.39, p = 0.01, n = 40) and burst strength and voltage amplitude (D3; r = 0.92, p<0.001, n = 40).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3475713&req=5

pone-0047940-g002: Distribution of cycle frequency and voltage amplitude for NMDA-induced membrane potential oscillations in Hb9 interneurons. A–B,Whole-cell current-clamp recordings of membrane potential from different Hb9 interneurons demonstrate variability of voltage amplitudes in NMDA induced oscillations. C1–3, Distribution plots of cycle frequency, voltage amplitude and burst strength. D1–3, There is no correlation between voltage amplitude and cycle frequency (D1; r = −0.10, p = 0.55, n = 40). However, correlations are found between burst strength and cycle frequency (D2; r = −0.39, p = 0.01, n = 40) and burst strength and voltage amplitude (D3; r = 0.92, p<0.001, n = 40).
Mentions: The properties of the TTX-resistant NMDA-induced oscillations were variable between Hb9 interneurons (Fig. 2A & B). To quantify this variability, we measured cycle frequency, voltage amplitude and burst strength from a common trough potential, held at −60 mV with bias current. The cycle frequency of NMDA-induced oscillations ranged from 0.34 to 0.95 Hz (mean  = 0.61±0.15 Hz, n = 40; Fig. 2C1). The voltage amplitude of NMDA induced oscillations ranged from 1.9 to 41.2 mV (mean  = 12.8±9.5 mV, n = 40; Fig. 2C2) with 70% (28 of 40) less than 15 mV. The burst strength of NMDA-induced oscillations ranged from 0.9 to 25.3 mV*sec (mean  = 7.2±5.9 mV*sec, n = 40; Fig. 2C3) with 75% (30 of 40) less than 10 mV*sec. These values do not show a bimodal distribution, suggesting that they reflect variation of a single population of Hb9 neurons.

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