scholarly journals Descending Influences on Vestibulospinal and Vestibulosympathetic Reflexes

2017 ◽  
Vol 8 ◽  
Author(s):  
Andrew A. McCall ◽  
Derek M. Miller ◽  
Bill J. Yates
Keyword(s):  
Descending Influences ◽  
Vestibulosympathetic Reflexes

Anatomic patterning in the expression of vestibulosympathetic reflexes

2000 ◽  
Vol 279 (1) ◽  
pp. R109-R117 ◽  
Author(s):  
I. A. Kerman ◽  
B. J. Yates ◽  
R. M. McAllen
Keyword(s):  
Relative Proportion ◽  
Vestibular Stimulation ◽  
Nerve Fibers ◽  
Spike Shape ◽  
The Face ◽  
Nerve Fascicle ◽  
The Difference ◽  
Vestibulosympathetic Reflexes

To investigate the possibility that expression of vestibulosympathetic reflexes (VSR) is related to a nerve's anatomic location rather than its target organ, we compared VSR recorded from the same type of postganglionic fiber [muscle vasoconstrictor (MVC)] located at three different rostrocaudal levels: hindlimb, forelimb, and face. Experiments were performed on chloralose-anesthetized cats, and vestibular afferents were stimulated electrically. Single MVC unit activity was extracted by spike shape analysis of few-fiber recordings, and unit discrimination was confirmed by autocorrelation. Poststimulus time histogram analysis revealed that about half of the neurons were initially inhibited by vestibular stimulation (type 1 response), whereas the other MVC fibers were initially strongly excited (type 2 response). MVC units with types 1 and 2 responses were present in the same nerve fascicle. Barosensitivity was equivalent in the two groups, but fibers showing type 1 responses fired significantly faster than those giving type 2 responses (0.29 ± 0.04 vs. 0.20 ± 0.02 Hz). Nerve fibers with type 1 responses were most common in the hindlimb (21 of 29 units) and least common in the face (2 of 11 units), the difference in relative proportion being significant ( P < 0.05, χ2 test). These results support the hypothesis that VSR are anatomically patterned.

scholarly journals Glutamatergic Control Of A Pattern-Generating Central Nucleus In A Gymnotiform Fish

2021 ◽  
Author(s):  
Virginia Comas ◽  
Michel Borde
Keyword(s):  
Metabotropic Glutamate Receptor ◽  
Electric Organ ◽  
Central Nucleus ◽  
Receptor Subtypes ◽  
Pacemaker Cells ◽  
Metabotropic Glutamate ◽  
Vertebrate Model ◽  
Brainstem Slices ◽  
Descending Influences ◽  
Electric Organ Discharges

The activity of central pattern-generating networks (CPGs) may change under the control exerted by various neurotransmitters and modulators to adapt its behavioral outputs to different environmental demands. Although the mechanisms underlying this control have been well established in invertebrates, most of their synaptic and cellular bases are not yet well understood in vertebrates. Gymnotus omarorum, a pulse-type gymnotiform electric fish, provides a well-suited vertebrate model to investigate these mechanisms. G. omarorum emits rhythmic and stereotyped electric organ discharges (EODs), which function in both perception and communication, under the command of an electromotor CPG. This nucleus is composed of electrotonically coupled intrinsic pacemaker cells, which pace the rhythm, and bulbospinal projecting relay cells that contribute to organize the pattern of the muscle-derived effector activation that produce the EOD. Descending influences target CPG neurons to produce adaptive behavioral electromotor responses to different environmental challenges. We used electrophysiological and pharmacological techniques in brainstem slices of G. omarorum to investigate the underpinnings of the fast transmitter control of its electromotor CPG. We demonstrate that pacemaker, but not relay cells, are endowed with ionotropic and metabotropic glutamate receptor subtypes. We also show that glutamatergic control of the CPG likely involves two types of synapses contacting pacemaker cells, one type containing both AMPAR-NMDAR receptors and the other one only-NMDAR. Fast neurotransmitter control of vertebrate CPGs seems to exploit the kinetics of the involved postsynaptic receptors to command different behavioral outputs. The prospect of common neural designs to control CPG activity in vertebrates is discussed.

Neuroanatomical, neurochemical, and neurophysiological bases of waking and sleeping

2017 ◽  
Author(s):  
Barbara E. Jones
Keyword(s):  
Slow Wave Sleep ◽  
Muscle Tone ◽  
Paradoxical Sleep ◽  
Cortical Activity ◽  
Cortical Activation ◽  
Behavioral Arousal ◽  
Distinct Cell ◽  
Cell Groups ◽  
Descending Influences ◽  
And Behavior

Neurons distributed through the reticular core of the brainstem, hypothalamus, and basal forebrain and giving rise to ascending projections to the cortex or descending projections to the spinal cord promote the changes in cortical activity and behavior that underlie the sleep–wake cycle and three states of waking, NREM (slow wave) sleep, and REM (paradoxical) sleep. Forming the basic units of these systems, glutamate and GABA cell groups are heterogeneous in discharge profiles and projections, such that different subgroups can promote cortical activation (wake/REM(PS)-active) versus cortical deactivation (NREM(SWS)-active) by ascending influences or behavioral arousal with muscle tone (wake-active) versus behavioral quiescence with muscle atonia (NREM/REM(PS)-active) by descending influences. These different groups are in turn regulated by neuromodulatory systems, including cortical activation (wake/REM(PS)-active acetylcholine neurons), behavioral arousal (wake-active noradrenaline, histamine, serotonin, and orexin neurons), and behavioral quiescence (NREM/REM(PS)-active MCH neurons). By different projections, chemical neurotransmitters and discharge profiles, distinct cell groups thus act and interact to promote cyclic oscillations in cortical activity and behavior forming the sleep-wake cycle and states.

Excitatory connections between upper cervical inspiratory neurons and phrenic motoneurons in cats

1994 ◽  
Vol 77 (2) ◽  
pp. 679-683 ◽  
Author(s):  
Y. Nakazono ◽  
M. Aoki
Keyword(s):  
Phrenic Nerve ◽  
Respiratory Neurons ◽  
Transmission Delays ◽  
Phrenic Motoneurons ◽  
Inspiratory Neurons ◽  
Upper Cervical ◽  
Cervical Segment ◽  
Focal Cooling ◽  
Descending Influences ◽  
Phrenic Motoneuron

This study aimed to determine whether upper cervical inspiratory neurons (UCINs), which are localized in the intermediolateral part of the gray matter of the upper cervical segments, have propriospinal connections to phrenic motoneurons of the ipsilateral lower cervical segment in anesthetized cats. Unit action potentials of UCINs were extracellularly recorded simultaneously with ipsilateral phrenic nerve activity. To eliminate the descending influences from medullary respiratory neurons to phrenic motoneurons, bulbospinal conduction paths were temporarily blocked by focal cooling applied to the ventral caudal medulla at the pyramidal decussation level by means of a cooling thermode (1 mm tip diam). By using a spike-triggered method, during cooling phrenic nerve activities were evoked by UCIN spikes that were elicited by microinjection of L-glutamate for 20 of the 55 (36%) UCIN units examined. The onset latencies of these phrenic motoneuron responses ranged from 1.5 to 7.1 ms (mean 3.6 ms), depending on synaptic transmission delays. These results clearly demonstrate that UCINs have, at least in part, excitatory mono- and paucisynaptic connections with ipsilateral phrenic motoneurons.

Modulation of Noxious and Non-Noxious Spinal Mechanical Transmission From the Rostral Medial Medulla in the Rat

2002 ◽  
Vol 88 (6) ◽  
pp. 2928-2941 ◽  
Author(s):  
M. Zhuo ◽  
G. F. Gebhart
Keyword(s):  
Electrical Stimulation ◽  
Mechanical Stimulation ◽  
Spinal Neuron ◽  
Noxious Stimulation ◽  
Mechanical Transmission ◽  
Inhibitory Effects ◽  
Stimulus Response ◽  
Hind Foot ◽  
Descending Influences ◽  
Noxious Mechanical Stimulation

Modulatory influences on spinal mechanical transmission from the rostral medial medulla (RMM) were studied. Noxious stimulation, produced by von Frey-like monofilaments, and non-noxious stimulation, produced by a soft brush, was applied to the glabrous skin of the hind foot. At 28 sties in RMM, electrical stimulation facilitated responses to noxious mechanical stimulation at low intensities (5–25 μA) and inhibited responses of the same neurons at greater intensities (50–100 μA) of stimulation. At 24 and 9 other sites in RMM, stimulation at all intensities only inhibited or only facilitated, respectively, responses to noxious mechanical stimulation of the hind foot. Stimulus-response functions to mechanical stimulation were shifted leftward by low intensities and decreased by high intensities of stimulation. Inhibitory influences were found to descend in the dorsolateral funiculi; facilitatory effects were contained in the ventral spinal cord. Descending modulation of non-noxious brush stimulation revealed biphasic facilitatory-inhibitory effects (9 sites in RMM), only inhibitory effects (14 sites) and only facilitatory effects (8 sites). The effects of electrical stimulation were replicated by intra-RMM administration of glutamate; a low concentration (0.25 nmol) facilitated and a greater concentration (2.5 nmol) inhibited spinal mechanical transmission, providing evidence that cells in RMM are sufficient to engage descending influences. Descending modulatory effects were specific for the site of stimulation, not for the spinal neuron, because modulation of the same neuron was different from different sites in RMM. These results show that spinal mechanical transmission, both noxious and non-noxious, is subject to descending influences, including facilitatory influences that may contribute to exaggerated responses to peripheral stimuli in some chronic pain states.

The role of some brain structures in the switching of the descending influences in operantly conditioned rats

Neuroscience ◽  
2000 ◽  
Vol 98 (2) ◽  
pp. 385-395 ◽  
Author(s):  
V.V. Fanardjian ◽  
E.V. Papoyan ◽  
E.A. Hovhannisyan ◽  
A.B. Melik-Moussian ◽  
O.V. Gevorkyan ◽  
...  
Keyword(s):  
Brain Structures ◽  
Descending Influences

Sympathetic and vascular responses to head-down neck flexion in humans

1997 ◽  
Vol 272 (4) ◽  
pp. H1780-H1784 ◽  
Author(s):  
T. L. Shortt ◽  
C. A. Ray
Keyword(s):  
Heart Rate ◽  
Arterial Pressure ◽  
Sympathetic Nerve ◽  
Muscle Sympathetic Nerve Activity ◽  
Systolic Arterial Pressure ◽  
Neck Flexion ◽  
Thoracic Impedance ◽  
Burst Frequency ◽  
Vascular Responses ◽  
Vestibulosympathetic Reflexes

Animal studies have demonstrated increases in sympathetic nerve outflow with vestibular stimulation. The purpose of the present study was to determine whether vestibulosympathetic reflexes are engaged in humans. Muscle sympathetic nerve activity (MSNA), heart rate, arterial pressure, calf blood flow (CBF), and calculated calf vascular resistance (CVR; mean arterial pressure/CBF) were determined during 10 min of baseline (laying prone with chin supported) and 10 min of head-down neck flexion (HDNF). MSNA responses were measured in nine subjects, and calf vascular responses were determined in seven of these subjects. Heart rate increased during the first minute of HDNF (71 +/- 2 to 76 +/- 3 beats/min; P < 0.05) and remained slightly elevated (71 +/- 2 to 74 +/- 3 beats/min; P < 0.05) for the duration of HDNF. Diastolic and mean arterial pressures also increased slightly with HDNF (80 +/- 3 to 82 +/- 3 and 96 +/- 3 to 98 +/- 3 mmHg, respectively; P < 0.05). Systolic arterial pressure did not change significantly during HDNF. CBF decreased 14% (4.63 +/- 0.78 to 3.97 +/- 0.60 ml x min(-1) x 100 ml(-1); P < 0.05), and CVR increased 12% (24.0 +/- 4.3 to 27.4 +/- 4.7 units; P < 0.05) during HDNF. These changes corresponded with significant increases in MSNA during HDNF. MSNA, expressed as burst frequency, increased from 14 +/- 2 to 20 +/- 2 bursts/min (P < 0.05) and increased 63 +/- 23% (P < 0.05) when expressed as the percent change in total activity. All variables returned to baseline during recovery. Thoracic impedance measured in five subjects did not change during HDNF (19.6 +/- 1.2 to 19.7 +/- 1.5 omega), suggesting no major change in central blood volume. The results indicate that HDNF elicits increases in CVR that are mediated by the augmentation of MSNA. Arterial pressure responses and thoracic impedance data suggest that high and low pressure baroreflexes were not the mechanism for sympathetic activation. The immediate increase in MSNA with HDNF suggests a role for vestibulosympathetic reflexes.

scholarly journals Glutamatergic Control Of A Pattern-Generating Central Nucleus In A Gymnotiform Fish

2020 ◽  
Author(s):  
Virginia Comas ◽  
Michel Borde
Keyword(s):  
Metabotropic Glutamate Receptors ◽  
Electric Organ ◽  
Central Nucleus ◽  
Pacemaker Cells ◽  
Social Challenges ◽  
Metabotropic Glutamate ◽  
Descending Influences ◽  
Electric Organ Discharges ◽  
Gymnotiform Fish

ABSTRACTThe activity of pattern-generating networks (CPG) may change under the control exerted by various neurotransmitters and modulators to adapt its behavioral outputs to different environmental demands. Although the mechanisms underlying this control have been well established in invertebrates, most of their synaptic and cellular bases are not yet well understood in vertebrates. Gymnotus omarorum, a pulse-type gymnotiform electric fish, provides a well-suited vertebrate model to investigate these mechanisms. G. omarorum emits rhythmic and stereotyped electric organ discharges (EODs), which function in both perception and communication. The EOD is considered the behavioral output of an electromotor CPG which, modulated by descending influences, organizes adaptive electromotor behaviors in response to environmental and social challenges. The CPG is composed of electrotonically coupled intrinsic pacemaker cells, which pace the rhythm, and bulbospinal projecting relay cells that contribute to organize the pattern of the muscle-derived effector activation that produce the EOD. We used electrophysiological and pharmacological techniques in brainstem slices of G. omarorum to investigate the underpinnings of the fast transmitter control of its electromotor CPG. We demonstrate that pacemaker, but not relay cells, are endowed with ionotropic and metabotropic glutamate receptors subtypes. We also show, for the first time in gymnotiformes, that glutamatergic control of the CPG likely involves both AMPA-NMDA receptors transmitting and only-NMDA segregated synapses contacting pacemaker cells. Our data shed light on the fast neurotransmitter control of a vertebrate CPG that seems to exploit the kinetics of the involved postsynaptic receptors to command different behavioral outputs.NEW & NOTEWORTHYUnderpinnings of neuromodulation of pattern-generating central networks (CPG) have been well characterized in many species. The effects of fast neurotransmitter systems remain, however, poorly understood. This research uses in vitro electrophysiological and pharmacological techniques to show that the neurotransmitter control of a vertebrate CPG in gymnotiform fish involve the convergence of only-NMDA and AMPA-NMDA glutamatergic synapses onto neurons that pace the rhythm. These inputs may organize different behavioral outputs according to their distinct functional properties.

Sign in / Sign up

Export Citation Format

Share Document