Serotonin is found in myelinated axons of the dorsolateral funiculus in monkeys

Karin N. Westlund, Ying Lu, Richard E. Coggeshall, William D. Willis

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

Physiological measurements suggest that the inhibition of primate spinothalamic tract cells by serotonin is mediated by myelinated axons. Previous morphologic studies emphasize that most serotonin-containing axons in the spinal cord are unmyelinated. Accordingly, the possibility that some serotonin-containing axons in the primate dorsolateral funiculus of the spinal cord are myelinated was investigated. Macaque monkeys were given l-tryptophan and the monoamine oxidase inhibitor, nialamide, intraperitoneally 1 h prior to sacrifice to increase axonal stores of serotonin. The animals were perfused (0.05 or 0.5% glutaraldehyde, 4% paraformaldehyde), and transverse sections of the thoracic cord were reacted with antibody against serotonin and then prepared for electron microscopy. Many of the immunostained axons in the dorsolateral funiculus included fine, myelinated fibers with diameters of 0.7-2.2 μm. Unmyelinated serotonin-containing axons were also observed. The observation of myelinated serotonin-containing axons in the white matter of the monkey dorsolateral funiculus contradicts the view that the descending serotoninergic projection consists entirely of unmyelinated fibers, particularly since the conduction velocity of the fine fibers would be too slow to account for the earliest latency of descending inhibition following stimulation in the brainstem. The presence of myelinated serotoninergic axons presumably accounts for the latencies reported for the inhibition of primate spinothalamic cells following stimulation of the periaqueductal gray, an inhibition that can be blocked with serotonin antagonists and that is associated with the release of serotonin in the dorsal horn.

Original languageEnglish (US)
Pages (from-to)35-38
Number of pages4
JournalNeuroscience Letters
Volume141
Issue number1
DOIs
StatePublished - Jul 6 1992

Fingerprint

Haplorhini
Axons
Serotonin
Primates
Spinal Cord
Spinothalamic Tracts
Nialamide
Periaqueductal Gray
Serotonin Antagonists
Monoamine Oxidase Inhibitors
Macaca
Glutaral
Tryptophan
Brain Stem
Electron Microscopy
Observation
Antibodies

Keywords

  • Electron microscopy
  • Pain
  • Primate
  • Raphe magnus
  • Reticular formation
  • Spinal cord

ASJC Scopus subject areas

  • Neuroscience(all)

Cite this

Serotonin is found in myelinated axons of the dorsolateral funiculus in monkeys. / Westlund, Karin N.; Lu, Ying; Coggeshall, Richard E.; Willis, William D.

In: Neuroscience Letters, Vol. 141, No. 1, 06.07.1992, p. 35-38.

Research output: Contribution to journalArticle

Westlund, Karin N. ; Lu, Ying ; Coggeshall, Richard E. ; Willis, William D. / Serotonin is found in myelinated axons of the dorsolateral funiculus in monkeys. In: Neuroscience Letters. 1992 ; Vol. 141, No. 1. pp. 35-38.
@article{1199fef1b4bc48dfbab7a104bb652580,
title = "Serotonin is found in myelinated axons of the dorsolateral funiculus in monkeys",
abstract = "Physiological measurements suggest that the inhibition of primate spinothalamic tract cells by serotonin is mediated by myelinated axons. Previous morphologic studies emphasize that most serotonin-containing axons in the spinal cord are unmyelinated. Accordingly, the possibility that some serotonin-containing axons in the primate dorsolateral funiculus of the spinal cord are myelinated was investigated. Macaque monkeys were given l-tryptophan and the monoamine oxidase inhibitor, nialamide, intraperitoneally 1 h prior to sacrifice to increase axonal stores of serotonin. The animals were perfused (0.05 or 0.5{\%} glutaraldehyde, 4{\%} paraformaldehyde), and transverse sections of the thoracic cord were reacted with antibody against serotonin and then prepared for electron microscopy. Many of the immunostained axons in the dorsolateral funiculus included fine, myelinated fibers with diameters of 0.7-2.2 μm. Unmyelinated serotonin-containing axons were also observed. The observation of myelinated serotonin-containing axons in the white matter of the monkey dorsolateral funiculus contradicts the view that the descending serotoninergic projection consists entirely of unmyelinated fibers, particularly since the conduction velocity of the fine fibers would be too slow to account for the earliest latency of descending inhibition following stimulation in the brainstem. The presence of myelinated serotoninergic axons presumably accounts for the latencies reported for the inhibition of primate spinothalamic cells following stimulation of the periaqueductal gray, an inhibition that can be blocked with serotonin antagonists and that is associated with the release of serotonin in the dorsal horn.",
keywords = "Electron microscopy, Pain, Primate, Raphe magnus, Reticular formation, Spinal cord",
author = "Westlund, {Karin N.} and Ying Lu and Coggeshall, {Richard E.} and Willis, {William D.}",
year = "1992",
month = "7",
day = "6",
doi = "10.1016/0304-3940(92)90328-5",
language = "English (US)",
volume = "141",
pages = "35--38",
journal = "Neuroscience Letters",
issn = "0304-3940",
publisher = "Elsevier Ireland Ltd",
number = "1",

}

TY - JOUR

T1 - Serotonin is found in myelinated axons of the dorsolateral funiculus in monkeys

AU - Westlund, Karin N.

AU - Lu, Ying

AU - Coggeshall, Richard E.

AU - Willis, William D.

PY - 1992/7/6

Y1 - 1992/7/6

N2 - Physiological measurements suggest that the inhibition of primate spinothalamic tract cells by serotonin is mediated by myelinated axons. Previous morphologic studies emphasize that most serotonin-containing axons in the spinal cord are unmyelinated. Accordingly, the possibility that some serotonin-containing axons in the primate dorsolateral funiculus of the spinal cord are myelinated was investigated. Macaque monkeys were given l-tryptophan and the monoamine oxidase inhibitor, nialamide, intraperitoneally 1 h prior to sacrifice to increase axonal stores of serotonin. The animals were perfused (0.05 or 0.5% glutaraldehyde, 4% paraformaldehyde), and transverse sections of the thoracic cord were reacted with antibody against serotonin and then prepared for electron microscopy. Many of the immunostained axons in the dorsolateral funiculus included fine, myelinated fibers with diameters of 0.7-2.2 μm. Unmyelinated serotonin-containing axons were also observed. The observation of myelinated serotonin-containing axons in the white matter of the monkey dorsolateral funiculus contradicts the view that the descending serotoninergic projection consists entirely of unmyelinated fibers, particularly since the conduction velocity of the fine fibers would be too slow to account for the earliest latency of descending inhibition following stimulation in the brainstem. The presence of myelinated serotoninergic axons presumably accounts for the latencies reported for the inhibition of primate spinothalamic cells following stimulation of the periaqueductal gray, an inhibition that can be blocked with serotonin antagonists and that is associated with the release of serotonin in the dorsal horn.

AB - Physiological measurements suggest that the inhibition of primate spinothalamic tract cells by serotonin is mediated by myelinated axons. Previous morphologic studies emphasize that most serotonin-containing axons in the spinal cord are unmyelinated. Accordingly, the possibility that some serotonin-containing axons in the primate dorsolateral funiculus of the spinal cord are myelinated was investigated. Macaque monkeys were given l-tryptophan and the monoamine oxidase inhibitor, nialamide, intraperitoneally 1 h prior to sacrifice to increase axonal stores of serotonin. The animals were perfused (0.05 or 0.5% glutaraldehyde, 4% paraformaldehyde), and transverse sections of the thoracic cord were reacted with antibody against serotonin and then prepared for electron microscopy. Many of the immunostained axons in the dorsolateral funiculus included fine, myelinated fibers with diameters of 0.7-2.2 μm. Unmyelinated serotonin-containing axons were also observed. The observation of myelinated serotonin-containing axons in the white matter of the monkey dorsolateral funiculus contradicts the view that the descending serotoninergic projection consists entirely of unmyelinated fibers, particularly since the conduction velocity of the fine fibers would be too slow to account for the earliest latency of descending inhibition following stimulation in the brainstem. The presence of myelinated serotoninergic axons presumably accounts for the latencies reported for the inhibition of primate spinothalamic cells following stimulation of the periaqueductal gray, an inhibition that can be blocked with serotonin antagonists and that is associated with the release of serotonin in the dorsal horn.

KW - Electron microscopy

KW - Pain

KW - Primate

KW - Raphe magnus

KW - Reticular formation

KW - Spinal cord

UR - http://www.scopus.com/inward/record.url?scp=0026765368&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0026765368&partnerID=8YFLogxK

U2 - 10.1016/0304-3940(92)90328-5

DO - 10.1016/0304-3940(92)90328-5

M3 - Article

VL - 141

SP - 35

EP - 38

JO - Neuroscience Letters

JF - Neuroscience Letters

SN - 0304-3940

IS - 1

ER -