Contribution of noradrenergic inputs to hypoglossal motoneuron (IHMN) activity in decerebrate dogs

We tested the hypothesis that phrenic and hypoglossal responses to progressive hypercapnia differ qualitatively because the CO2-related drive inputs to their respective motoneuron pools are different. The relative contributions of carotid sinus and central chemoreceptor inputs to hypoglossal and phrenic responses during hyperoxic hypercapnia were determined by comparing the two nerve activities during rebreathing runs done either before and after bilateral carotid sinus nerve (CSN) section, or without and with cooling of the intermediate, I(s), area on the ventral surface of the medulla. The studies were performed on chloralose-anesthetized, vagotomized, paralyzed cats. Cooling of the I(s) area impaired phrenic responsiveness to hypercapnia more than hypoglossal responsiveness, whereas CSN section had the opposite effect. Thus phrenic nerve response was more dependent on central chemoreceptor input than was the hypoglossal response, but hypoglossal response was more dependent on carotid sinus chemoreceptor input. We conclude that the phrenic and hypoglossal motoneuron pools each receive a different functional input from both the medullary and the carotid sinus chemoreceptors.

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0066 Glycinergic Postsynaptic Inhibition is Responsible for the Suppression of Hypoglossal Motoneuron Activity During Naturally-Occurring REM Sleep

SLEEP ◽

10.1093/sleep/zsaa056.064 ◽

2020 ◽

Vol 43 (Supplement_1) ◽

pp. A27-A27

Author(s):

C Tobin ◽

S J Fung ◽

M Xi ◽

M H Chase

Keyword(s):

Rem Sleep ◽

Hypoglossal Nerve ◽

Nrem Sleep ◽

T Test ◽

Hypoglossal Nucleus ◽

Postsynaptic Inhibition ◽

Nerve Activity ◽

Naturally Occurring ◽

Hypoglossal Motoneuron ◽

Motoneuron Activity

Abstract Introduction The present study was undertaken to explore the role of glycinergic postsynaptic inhibition and monoaminergic disfacilitation (a withdrawal of excitatory noradrenergic and serotonergic inputs) in the control of hypoglossal motoneuron activity during REM sleep. Accordingly, glycinergic, noradrenergic and serotonergic antagonists were microinjected into the hypoglossal nucleus, and their effects on the hypoglossal nerve activity during REM sleep were examined in chronically-instrumented, unanesthetized cats. Methods Adults cats were prepared for monitoring behavioral states of sleep and wakefulness, and for extracellular recordings from hypoglossal nerve. Strychnine (a glycinergic antagonist) and a mixture of prazosin (a noradrenergic antagonist) and methysergide (a serotonergic antagonist) were microinjected, separately, into the hypoglossal nucleus during naturally-occurring states of sleep and wakefulness. Results During REM sleep, compared to non-REM sleep, the hypoglossal nerve activity decreased by 17.4±1.5% (n=17) in the control recordings (prior to the injection of strychnine). Following the microinjection of strychnine, there was only a mean decrease of 7.2±1.2% (n=12) in the nerve activity during REM sleep versus NREM sleep. The strychnine effect was statistically significant compared to control (p<0.001; unpaired t-test), which indicates that strychnine blocks REM sleep-related suppression of hypoglossal nerve activity. In contrast, the microinjection of prazosin and methysergide did not significantly reduce the hypoglossal nerve activity during REM sleep (control: 15.9±2.3, n=9 vs. prazosin+methysergide: 12.6±1.4%, n=10, p=0.229, unpaired t-test). Conclusion The present results demonstrate that the microapplication of strychnine, but not prazosin and methysergide, into the hypoglossal nucleus significantly reduces the suppression of the hypoglossal nerve activity during naturally-occurring REM sleep. We therefore suggest that glycinergic postsynaptic inhibition is primarily responsible for the suppression of hypoglossal motoneuron activity during REM sleep. Support 5R01NS094062

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Incorporation of realistic intracellular calcium (Ca 2+ ) dynamics into a hypoglossal motoneuron computational model

The FASEB Journal ◽

10.1096/fasebj.26.1_supplement.1147.4 ◽

2012 ◽

Vol 26 (S1) ◽

Author(s):

Kyle Graham Horn ◽

Irene C. Solomon

Keyword(s):

Computational Model ◽

Intracellular Calcium ◽

Hypoglossal Motoneuron

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Developmental changes in hypoglossal motoneuron morphology in neonatal rat

The FASEB Journal ◽

10.1096/fasebj.2018.32.1_supplement.742.3 ◽

2018 ◽

Vol 32 (S1) ◽

Author(s):

Paul Allen Williams ◽

Denise Bellinger ◽

Christopher G. Wilson

Keyword(s):

Developmental Changes ◽

Neonatal Rat ◽

Hypoglossal Motoneuron

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Synchronization of presynaptic input to motor units of tongue, inspiratory intercostal, and diaphragm muscles

Journal of Neurophysiology ◽

10.1152/jn.01078.2010 ◽

2011 ◽

Vol 105 (5) ◽

pp. 2330-2336 ◽

Cited By ~ 17

Author(s):

Amber Rice ◽

Andrew J. Fuglevand ◽

Christopher M. Laine ◽

Ralph F. Fregosi

Keyword(s):

Motor Neuron ◽

Motor Unit ◽

Motor Units ◽

Excitatory Input ◽

Respiratory Drive ◽

Tongue Muscle ◽

Motoneuron Pool ◽

Hypoglossal Motoneuron ◽

Tongue Muscles ◽

Premotor Neurons

The respiratory central pattern generator distributes rhythmic excitatory input to phrenic, intercostal, and hypoglossal premotor neurons. The degree to which this input shapes motor neuron activity can vary across respiratory muscles and motor neuron pools. We evaluated the extent to which respiratory drive synchronizes the activation of motor unit pairs in tongue (genioglossus, hyoglossus) and chest-wall (diaphragm, external intercostals) muscles using coherence analysis. This is a frequency domain technique, which characterizes the frequency and relative strength of neural inputs that are common to each of the recorded motor units. We also examined coherence across the two tongue muscles, as our previous work shows that, despite being antagonists, they are strongly coactivated during the inspiratory phase, suggesting that excitatory input from the premotor neurons is distributed broadly throughout the hypoglossal motoneuron pool. All motor unit pairs showed highly correlated activity in the low-frequency range (1–8 Hz), reflecting the fundamental respiratory frequency and its harmonics. Coherence of motor unit pairs recorded either within or across the tongue muscles was similar, consistent with broadly distributed premotor input to the hypoglossal motoneuron pool. Interestingly, motor units from diaphragm and external intercostal muscles showed significantly higher coherence across the 10–20-Hz bandwidth than tongue-muscle units. We propose that the lower coherence in tongue-muscle motor units over this range reflects a larger constellation of presynaptic inputs, which collectively lead to a reduction in the coherence between hypoglossal motoneurons in this frequency band. This, in turn, may reflect the relative simplicity of the respiratory drive to the diaphragm and intercostal muscles, compared with the greater diversity of functions fulfilled by muscles of the tongue.

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