Direct pathway from cardiovascular neurons in the ventrolateral medulla to the region of the intermediolateral nucleus of the upper thoracic cord: an anatomical and electrophysiological investigation in the cat

Recording experiments were done in chloralose-anesthetized, paralyzed, and artificially ventilated cats to identify single units in the ventrolateral medulla (VLM) projecting directly to the region of the intermediolateral nucleus of the spinal cord (T2) and responding to selective activation of peripheral chemoreceptors (sodium cyanide, 20-60 micrograms in 0.1-0.3 ml saline into medial thyroid artery) and baroreceptors (phenylephrine, 2 micrograms/kg iv). The firing frequency of 49 of the 81 antidromically identified single units was altered by activation of the peripheral cardiovascular receptors. Of these responsive units, 25 responded only to activation of chemoreceptors (17 excited and 8 inhibited), 20 responded in various combinations to activation of both chemo- and baroreceptors, and 4 responded only to activation of baroreceptors. In addition, units that altered their firing frequency during baroreceptor activation (n = 24) responded in the opposite direction to baroreceptor unloading (carotid arterial occlusion). These results suggest that neurons in the VLM are components of bulbospinal sympathoexcitatory and -inhibitory pathways that receive cardiovascular afferent information and in turn influence vasoconstrictor and cardioacceleratory neurons in the intermediolateral nucleus of the upper thoracic cord.

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Loss of intermediolateral nucleus in the upper thoracic cord increase risk of sudden cardiac arrest in ALS

Autonomic Neuroscience ◽

10.1016/j.autneu.2007.06.238 ◽

2007 ◽

Vol 135 (1-2) ◽

pp. 136

Author(s):

Hirohide Asai ◽

Makito Hirano ◽

Fukashi Udaka ◽

Yoshiko Furiya ◽

Keiji Shimada ◽

...

Keyword(s):

Cardiac Arrest ◽

Sudden Cardiac Arrest ◽

Increase Risk ◽

Thoracic Cord ◽

Upper Thoracic ◽

Intermediolateral Nucleus

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Contribution of α2-adrenoceptors in caudal ventrolateral medulla to cardiovascular regulation in rat

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1998.274.4.r1119 ◽

1998 ◽

Vol 274 (4) ◽

pp. R1119-R1124 ◽

Cited By ~ 3

Author(s):

Shogo Sesoko ◽

Hiromi Muratani ◽

Masanobu Yamazato ◽

Hiroshi Teruya ◽

Shuichi Takishita ◽

...

Keyword(s):

Cardiovascular Effect ◽

Ventrolateral Medulla ◽

Sprague Dawley ◽

Renal Sympathetic Nerve Activity ◽

Caudal Ventrolateral Medulla ◽

Adrenoceptor Antagonist ◽

Sprague Dawley Rats ◽

Artificial Cerebrospinal Fluid ◽

Cardiovascular Neurons ◽

Selective Blocker

The inhibitory action of α2-agonists on the cardiovascular neurons has been elucidated in the rostral ventrolateral medulla (RVLM) but not in the caudal ventrolateral medulla (CVLM). Our study aimed to clarify whether microinjection of clonidine into the CVLM elicits any cardiovascular effect and whether endogenous α2-adrenoceptor-mediated mechanisms contribute to the tonic activity of the CVLM neurons. In male Sprague-Dawley rats (7–9 wk old, 270–320 g) anesthetized with urethan, unilateral microinjection of 8 nmol of clonidine into the CVLM ( n = 10) increased mean arterial pressure (MAP) and renal sympathetic nerve activity (RSNA) by 12.1 ± 1.8 mmHg (mean ± SE, P < 0.01) and 25.8 ± 4.8% ( P < 0.01), while heart rate (HR) remained unaltered. Unilateral microinjection of 2 nmol of SKF-86466, a selective blocker of the α2-adrenoceptors, into the CVLM ( n = 10) decreased MAP, HR, and RSNA (−11.6 ± 2.6 mmHg, −26 ± 7 beats/min, and −15.3 ± 1.7%, respectively, P < 0.01 for each). Artificial cerebrospinal fluid caused neither a cardiovascular effect nor a sympathetic response. Prior injection of SKF-86466 into the ipsilateral CVLM attenuated the effects of clonidine. Bilateral microinjection of muscimol into the RVLM abolished the effects of both clonidine and SKF-86466 injected into the CVLM. The pressor and sympathoexcitatory effects of clonidine injected into the CVLM suggest a neuroinhibitory action of the drug on the CVLM neurons. In addition,the depressor and sympathoinhibitory effects of SKF-86466 injected into the CVLM indicated that activation of α2-adrenoceptors by endogenous ligand inhibits CVLM neurons. The effects of clonidine and the α2-adrenoceptor antagonist in the CVLM require the integrity of the RVLM.

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Distribution of glutamate- and GABA-immunoreactive neurons projecting to the cardioacceleratory center of the intermediolateral nucleus of the thoracic cord of SHR and WKY rats: a double-labeling study

Brain Research ◽

10.1016/0006-8993(94)90643-2 ◽

1994 ◽

Vol 638 (1-2) ◽

pp. 139-150 ◽

Cited By ~ 40

Author(s):

Mitsuhiko Miura ◽

Kiyoshige Takayama ◽

Junichi Okada

Keyword(s):

Double Labeling ◽

Wky Rats ◽

Thoracic Cord ◽

Shr And Wky Rats ◽

Intermediolateral Nucleus

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Distribution of glutamate- and GABA-immunoreactive neurons projecting to the vasomotor center of the intermediolateral nucleus of the lower thoracic cord of Wistar rats: a double-labeling study

Neuroscience Letters ◽

10.1016/0304-3940(94)90012-4 ◽

1994 ◽

Vol 174 (2) ◽

pp. 165-168 ◽

Cited By ~ 28

Author(s):

Masahiro Matsumoto ◽

Kiyoshige Takayama ◽

Mitsuhiko Miura

Keyword(s):

Wistar Rats ◽

Double Labeling ◽

Vasomotor Center ◽

Thoracic Cord ◽

Intermediolateral Nucleus

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Effects of substance P and thyrotropin-releasing hormone on sympathetic preganglionic neurones in the upper thoracic intermediolateral nucleus of the cat

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y84-038 ◽

1984 ◽

Vol 62 (2) ◽

pp. 248-251 ◽

Cited By ~ 116

Author(s):

S. B. Backman ◽

J. L. Henry

Keyword(s):

Substance P ◽

Synaptic Transmission ◽

Thyrotropin Releasing Hormone ◽

Excitatory Effect ◽

Releasing Hormone ◽

Spinal Segments ◽

Time Courses ◽

Upper Thoracic ◽

Intermediolateral Nucleus ◽

Chemical Mediators

When applied by iontophoresis onto single sympathetic preganglionic neurones in the intermediolateral nucleus of spinal segments T1–T3 in the cat, substance P and thyrotropin-releasing hormone (TRH) each had a weak excitatory effect. Two-thirds of the neurones studied were excited by substance P while one-fifth were excited by TRH. The time courses of the responses to substance P and to TRH were similar, and consisted of an increase in the rate of discharge with a latency of approximately 30 s from the onset of application. They were also prolonged (30–320 s) in afterdischarge following termination of application. These results indicate that substance P and TRH exert excitatory effects on single sympathetic preganglionic neurones, and support the possibility that they may be chemical mediators of synaptic transmission in the intermediolateral nucleus.

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