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Nitric oxide-mediated modulation of the murine locomotor network.

Foster JD, Dunford C, Sillar KT, Miles GB - J. Neurophysiol. (2013)

Bottom Line: The effects of DEA/NO were mimicked by the cGMP analog 8-bromo-cGMP.The number of NOS-positive cells was also found to increase during postnatal development.In summary, we have shown that NO, derived from sources within the mammalian spinal cord, modulates the output of spinal motor networks and is therefore likely to contribute to the fine-tuning of locomotor behavior.

View Article: PubMed Central - PubMed

Affiliation: School of Psychology and Neuroscience, University of St Andrews, St Andrews, Fife, United Kingdom.

ABSTRACT
Spinal motor control networks are regulated by neuromodulatory systems to allow adaptability of movements. The present study aimed to elucidate the role of nitric oxide (NO) in the modulation of mammalian spinal locomotor networks. This was investigated with isolated spinal cord preparations from neonatal mice in which rhythmic locomotor-related activity was induced pharmacologically. Bath application of the NO donor diethylamine NONOate (DEA/NO) decreased the frequency and modulated the amplitude of locomotor-related activity recorded from ventral roots. Removal of endogenous NO with coapplication of a NO scavenger (PTIO) and a nitric oxide synthase (NOS) blocker [nitro-l-arginine methyl ester (l-NAME)] increased the frequency and decreased the amplitude of locomotor-related activity. This demonstrates that endogenously derived NO can modulate both the timing and intensity of locomotor-related activity. The effects of DEA/NO were mimicked by the cGMP analog 8-bromo-cGMP. In addition, the soluble guanylyl cyclase (sGC) inhibitor ODQ blocked the effects of DEA/NO on burst amplitude and frequency, although the frequency effect was only blocked at low concentrations of DEA/NO. This suggests that NO-mediated modulation involves cGMP-dependent pathways. Sources of NO were studied within the lumbar spinal cord during postnatal development (postnatal days 1-12) with NADPH-diaphorase staining. NOS-positive cells in the ventral horn exhibited a rostrocaudal gradient, with more cells in rostral segments. The number of NOS-positive cells was also found to increase during postnatal development. In summary, we have shown that NO, derived from sources within the mammalian spinal cord, modulates the output of spinal motor networks and is therefore likely to contribute to the fine-tuning of locomotor behavior.

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The cGMP analog 8-bromo-cGMP mimics the effects of DEA/NO on the frequency and amplitude of locomotor-related activity. A: raw (top) and rectified/integrated (bottom) traces recorded from left and right L2 ventral roots showing the effect of 8-bromo-cGMP (200 μM). B: time course plots of normalized data aggregated into 1-min bins show an increase in amplitude (top) and a decrease in frequency (bottom) during 8-bromo-cGMP application. C: locomotor burst amplitude (Ci) and frequency (Cii) during a 5-min period in control, 8-bromo-cGMP application (15 min into drug application), and washout (25 min from start of washout). Individual data points are shown in gray, and mean is represented by black line. Statistically significant differences in pairwise comparisons: *P < 0.05, **P < 0.01, ***P < 0.001; n = 9.
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Figure 3: The cGMP analog 8-bromo-cGMP mimics the effects of DEA/NO on the frequency and amplitude of locomotor-related activity. A: raw (top) and rectified/integrated (bottom) traces recorded from left and right L2 ventral roots showing the effect of 8-bromo-cGMP (200 μM). B: time course plots of normalized data aggregated into 1-min bins show an increase in amplitude (top) and a decrease in frequency (bottom) during 8-bromo-cGMP application. C: locomotor burst amplitude (Ci) and frequency (Cii) during a 5-min period in control, 8-bromo-cGMP application (15 min into drug application), and washout (25 min from start of washout). Individual data points are shown in gray, and mean is represented by black line. Statistically significant differences in pairwise comparisons: *P < 0.05, **P < 0.01, ***P < 0.001; n = 9.

Mentions: NO-mediated signaling typically involves the activation of NO-sensitive sGC and the subsequent accumulation of intracellular cGMP that can act on a range of intracellular and membrane-bound targets (Ahern et al. 2002). To elucidate the signaling pathways involved in NO-mediated modulation of spinal locomotor circuitry, we assessed the effects of pharmacological agents that target sGC-mediated signaling pathways. We first investigated the effects of application of a stable and membrane-permeant analog of cGMP, 8-bromo-cGMP (200 μM), on locomotor-related activity recorded from the isolated spinal cord preparation. The application of 8-bromo-cGMP led to a reversible reduction in the frequency of locomotor-related activity (24.9 ± 5.6%; Fig. 3, A, B, and Cii; F[2,16] = 16.3, P < 0.001, n = 9) and a sustained increase in the amplitude of locomotor-related ventral root bursts (8.9 ± 2.6%; Fig. 3, A, B, and Ci; F[2, 16] = 8.4, P < 0.01, n = 9). The actions of 8-bromo-cGMP mimic the effects of the lower concentration of DEA/NO (50 μM; Fig. 1, Ai, Ci, Di, and Dii) and support involvement of the sGC/cGMP pathway in the modulatory actions of NO on the murine locomotor control network.


Nitric oxide-mediated modulation of the murine locomotor network.

Foster JD, Dunford C, Sillar KT, Miles GB - J. Neurophysiol. (2013)

The cGMP analog 8-bromo-cGMP mimics the effects of DEA/NO on the frequency and amplitude of locomotor-related activity. A: raw (top) and rectified/integrated (bottom) traces recorded from left and right L2 ventral roots showing the effect of 8-bromo-cGMP (200 μM). B: time course plots of normalized data aggregated into 1-min bins show an increase in amplitude (top) and a decrease in frequency (bottom) during 8-bromo-cGMP application. C: locomotor burst amplitude (Ci) and frequency (Cii) during a 5-min period in control, 8-bromo-cGMP application (15 min into drug application), and washout (25 min from start of washout). Individual data points are shown in gray, and mean is represented by black line. Statistically significant differences in pairwise comparisons: *P < 0.05, **P < 0.01, ***P < 0.001; n = 9.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3921400&req=5

Figure 3: The cGMP analog 8-bromo-cGMP mimics the effects of DEA/NO on the frequency and amplitude of locomotor-related activity. A: raw (top) and rectified/integrated (bottom) traces recorded from left and right L2 ventral roots showing the effect of 8-bromo-cGMP (200 μM). B: time course plots of normalized data aggregated into 1-min bins show an increase in amplitude (top) and a decrease in frequency (bottom) during 8-bromo-cGMP application. C: locomotor burst amplitude (Ci) and frequency (Cii) during a 5-min period in control, 8-bromo-cGMP application (15 min into drug application), and washout (25 min from start of washout). Individual data points are shown in gray, and mean is represented by black line. Statistically significant differences in pairwise comparisons: *P < 0.05, **P < 0.01, ***P < 0.001; n = 9.
Mentions: NO-mediated signaling typically involves the activation of NO-sensitive sGC and the subsequent accumulation of intracellular cGMP that can act on a range of intracellular and membrane-bound targets (Ahern et al. 2002). To elucidate the signaling pathways involved in NO-mediated modulation of spinal locomotor circuitry, we assessed the effects of pharmacological agents that target sGC-mediated signaling pathways. We first investigated the effects of application of a stable and membrane-permeant analog of cGMP, 8-bromo-cGMP (200 μM), on locomotor-related activity recorded from the isolated spinal cord preparation. The application of 8-bromo-cGMP led to a reversible reduction in the frequency of locomotor-related activity (24.9 ± 5.6%; Fig. 3, A, B, and Cii; F[2,16] = 16.3, P < 0.001, n = 9) and a sustained increase in the amplitude of locomotor-related ventral root bursts (8.9 ± 2.6%; Fig. 3, A, B, and Ci; F[2, 16] = 8.4, P < 0.01, n = 9). The actions of 8-bromo-cGMP mimic the effects of the lower concentration of DEA/NO (50 μM; Fig. 1, Ai, Ci, Di, and Dii) and support involvement of the sGC/cGMP pathway in the modulatory actions of NO on the murine locomotor control network.

Bottom Line: The effects of DEA/NO were mimicked by the cGMP analog 8-bromo-cGMP.The number of NOS-positive cells was also found to increase during postnatal development.In summary, we have shown that NO, derived from sources within the mammalian spinal cord, modulates the output of spinal motor networks and is therefore likely to contribute to the fine-tuning of locomotor behavior.

View Article: PubMed Central - PubMed

Affiliation: School of Psychology and Neuroscience, University of St Andrews, St Andrews, Fife, United Kingdom.

ABSTRACT
Spinal motor control networks are regulated by neuromodulatory systems to allow adaptability of movements. The present study aimed to elucidate the role of nitric oxide (NO) in the modulation of mammalian spinal locomotor networks. This was investigated with isolated spinal cord preparations from neonatal mice in which rhythmic locomotor-related activity was induced pharmacologically. Bath application of the NO donor diethylamine NONOate (DEA/NO) decreased the frequency and modulated the amplitude of locomotor-related activity recorded from ventral roots. Removal of endogenous NO with coapplication of a NO scavenger (PTIO) and a nitric oxide synthase (NOS) blocker [nitro-l-arginine methyl ester (l-NAME)] increased the frequency and decreased the amplitude of locomotor-related activity. This demonstrates that endogenously derived NO can modulate both the timing and intensity of locomotor-related activity. The effects of DEA/NO were mimicked by the cGMP analog 8-bromo-cGMP. In addition, the soluble guanylyl cyclase (sGC) inhibitor ODQ blocked the effects of DEA/NO on burst amplitude and frequency, although the frequency effect was only blocked at low concentrations of DEA/NO. This suggests that NO-mediated modulation involves cGMP-dependent pathways. Sources of NO were studied within the lumbar spinal cord during postnatal development (postnatal days 1-12) with NADPH-diaphorase staining. NOS-positive cells in the ventral horn exhibited a rostrocaudal gradient, with more cells in rostral segments. The number of NOS-positive cells was also found to increase during postnatal development. In summary, we have shown that NO, derived from sources within the mammalian spinal cord, modulates the output of spinal motor networks and is therefore likely to contribute to the fine-tuning of locomotor behavior.

Show MeSH
Related in: MedlinePlus