Journal ArticleDOI
Hypoventilation recruits preganglionic sympathetic fibers with inspiration-related activity in the superior cervical trunk of the rat.
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The findings suggest that the respiratory modulation of preganglionic sympathetic activity in the CST consists of expiration-related activity in normal acid-base status, which probably constitute a subgroup of sympathetic neurons which is activated under increased respiratory drive.Abstract:
Activity in preganglionic sympathetic neurons projecting in the cervical sympathetic trunk (CST) of rats was analysed with respect to changes in the pattern of the respiratory modulation during a long lasting hypoventilation. Under normal acid-base status (pH: 7.36+/-0.04, pCO2: 42.1+/-6.1 mm Hg, pO2: 135.8+/-43 mm Hg) a maximum of activity during expiration (expiration-related activity) was observed in all nerve recordings (n = 27). No other pattern of respiratory modulation was observed under this condition. Under a hypoventilation a dissociation between the duration of phrenic nerve activity and that of the inspiratory inhibition in neurons with expiration-related activity was observed as the inhibition was significantly prolonged by 49+/-24.9% and outlasted inspiration in 5/7 multifibers. When acid-base status was systematically changed (pH: 7.15+/-0.05, pCO2: 80.4+/-11.8 mm Hg, pO2: 62.8+/-17.5 mm Hg [n = 7]) by a hypoventilation lasting for several hours activity with a maximum peak during central inspiration (inspiration-related activity) emerged and disappeared when control conditions were reestablished. Neurons with expiration-related activity showed a cardiac rhythmicity (CR) of 62.5+/-14.6% (n = 27) and were inhibited to baroreceptor stimulation whereas neurons with inspiration-related activity showed no discernible CR (23.1+/-5.1%; n = 7) and were not inhibited to baroreceptor stimulation. Furthermore, expiration-related neurons were inhibited by 32.5+/-18.3% (n = 27) during noxious cutaneous stimulation while neurons with inspiration-related activity were activated by 21.5+/-12.1% (n = 7). These findings suggest that the respiratory modulation of preganglionic sympathetic activity in the CST consists of expiration-related activity in normal acid-base status. During hypoventilation neurons with inspiration-related activity are recruited. These neurons show reflex patterns distinct from expiration-related neurons and probably constitute a subgroup of sympathetic neurons which is activated under increased respiratory drive.read more
Citations
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Neurophysiological analysis of target-related sympathetic pathways--from animal to human: similarities and differences.
TL;DR: The similarities of the results obtained in the in vivo studies in the human and in animals justify concluding that the principles of the central organization of sympathetic systems are similar, if not identical, at least in the neuraxis, in both species.
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Sympathetic rhythms and nervous integration.
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Autonomic neural control of the airways.
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Rhythmic activities of the sympatho-excitatory neurons in the medulla of rabbits: neurons controlling cutaneous vasomotion.
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References
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Journal ArticleDOI
Response of the medullary respiratory network of the cat to hypoxia.
TL;DR: The results indicate that the medullary respiratory network is directly affected by energy depletion and there is indication for a neurohumoral mechanism which blocks synaptic interaction between respiratory neurones in chemoreceptor‐intact animals.
Journal ArticleDOI
Properties of presympathetic neurones in the rostral ventrolateral medulla in the rat: an intracellular study "in vivo'.
TL;DR: No evidence was found for the presence of gradual depolarizations (autodepolarizations) between individual action potentials, and therefore under these experimental conditions the activity of RVLM presympathetic neurones did not depend on intrinsic pacemaker properties.
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