Advanced

Immunocytochemical studies of excitatory amino acid neurotransmitters and transporters in the spinal cord and nucleus submedius

Persson, Stefan LU (2004)
Abstract (Swedish)
Popular Abstract in Swedish

Signaler om smärta och känsel löper från receptorer ute i kroppen genom olika typer av nervfibrer in till ryggmärgens bakhorn och till trigeminuskärnorna i hjärnstammen. Där kopplas signalerna via synapser vidare till nervceller som leder signalerna upp till hjärnan, så att vi blir medvetna om vad som händer i kroppen. På sin väg till hjärnbarken kopplas signalerna om ytterligare en gång i thalamus. Ett i sammanhanget speciellt intressant thalamusområde hos råtta är nucleus submedius. Denna kärna tar emot nervfibrer från den ytliga delen av trigeminuskärnan och har förbindelser till delar av hjärnbarken som är inblandade i känslomässiga reaktioner. Nucleus submedius har därför föreslagits vara en... (More)
Popular Abstract in Swedish

Signaler om smärta och känsel löper från receptorer ute i kroppen genom olika typer av nervfibrer in till ryggmärgens bakhorn och till trigeminuskärnorna i hjärnstammen. Där kopplas signalerna via synapser vidare till nervceller som leder signalerna upp till hjärnan, så att vi blir medvetna om vad som händer i kroppen. På sin väg till hjärnbarken kopplas signalerna om ytterligare en gång i thalamus. Ett i sammanhanget speciellt intressant thalamusområde hos råtta är nucleus submedius. Denna kärna tar emot nervfibrer från den ytliga delen av trigeminuskärnan och har förbindelser till delar av hjärnbarken som är inblandade i känslomässiga reaktioner. Nucleus submedius har därför föreslagits vara en viktig komponent i det att vi upplever smärta som obehagligt. Det finns starka belägg för att de synapser som överför smärt- eller känselsignaler i ryggmärgens bakhorn och i thalamus använder aminosyran glutamat som signalsubstans. En del studier talar för att även den närbesläktade aminosyran aspartat kan ha en sådan funktion just i smärtsynapserna. Vi försökte därför utröna om aspartat, i tillägg till glutamat, används som signalsubstans i känselfibrernas synapser i ryggmärgens bakhorn och i de uppåtstigande banornas synapser i nucleus submedius. För att karakterisera synapserna vidare studerade vi också vilken transportör som används för att anrika glutamat i de synapsblåsor där glutamatet förvaras innan den frisläpps i synapsen. Idag känner man till tre glutamattransportörer, VGLUT1, VGLUT2 och VGLUT3, av vilka de två första är de allra mest utbredda. För att studera dessa frågor använde vi ryggmärgs- och thalamussnitt, vilka färgades på olika sätt med antikroppar som specifikt binder till de olika undersökta substanserna. Undersökningarna visade att glutamat förekommer i höga koncentrationer i nervändsluten i både ryggmärgen och nucleus submedius, medan koncentrationerna av aspartat är tämligen låga i båda områdenas nervändslut. Våra fynd talar också för att glutamat, men inte aspartat, är anrikat i nervändslutens synapsblåsor. Fynden stödjer således att glutamat fungerar som signalsubstans i dessa nervändslut, medan däremot aspartat troligen ej frisätts som signalsubstans utan enbart har en roll i nervändslutens ämnesomsättning. Våra fynd visar också att de tjocka nervfibrer som leder beröringssignaler från huden till de djupa delarna av bakhornet fr a använder VGLUT1 för att lagra glutamat i sina synapsblåsor. De tunnare smärtfibrernas nervändslut i bakhornets ytliga delar använder istället troligen VGLUT2. Lagring av glutamat i trigeminusfibrernas nervändslut i nucleus submedius medieras fr a av VGLUT2, medan andra glutamatfrisättande nervändslut i kärnan, med troligt ursprung från hjärnbarken, använder VGLUT1. (Less)
Abstract
The amino acid glutamate is today regarded as the main fast excitatory neurotransmitter in the central nervous system and a large body of evidence support that glutamate serves as a neurotransmitter in primary afferent terminals in the spinal cord. Previous evidence also suggests that the closely related amino acid aspartate may serve a similar role in some primary afferent terminals. However, the present quantitative analysis of aspartate immunogold labeling show that primary afferent terminals in both the superficial and deep laminae of the dorsal horn contain only low levels of aspartate. Further, whereas glutamate immunogold labeling density demonstrated a positive correlation with synaptic vesicle density in primary afferent... (More)
The amino acid glutamate is today regarded as the main fast excitatory neurotransmitter in the central nervous system and a large body of evidence support that glutamate serves as a neurotransmitter in primary afferent terminals in the spinal cord. Previous evidence also suggests that the closely related amino acid aspartate may serve a similar role in some primary afferent terminals. However, the present quantitative analysis of aspartate immunogold labeling show that primary afferent terminals in both the superficial and deep laminae of the dorsal horn contain only low levels of aspartate. Further, whereas glutamate immunogold labeling density demonstrated a positive correlation with synaptic vesicle density in primary afferent terminals, no such correlation was evident in aspartate immunogold labeled sections. Thus, aspartate is likely to serve a metabolic role but not a neurotransmitter role in primary afferent terminals. Immunolabeling of spinal cord sections with antisera against the vesicular glutamate transporters VGLUT1 and VGLUT2 showed distribution patterns of immunolabeled varicosities consistent with an expression of mainly VGLUT2 in small caliber primary afferent fibers and of mainly VGLUT1 in large caliber primary afferent fibers. The latter suggestion was confirmed by demonstration of VGLUT1 in anterogradely labeled varicosities originating from large caliber primary afferent fibers. VGLUT1 was also detected in fibers of the corticospinal tract and in small varicosities in the spinal grey matter likely to originate from these fibers. VGLUT2 immunolabeled varicosities were distributed throughout the spinal gray matter. In addition to an origin from small caliber primary afferent fibers, such varicosities are likely to originate from intraspinal and bulbospinal neurons. The signals transmitted by primary afferent terminals are relayed through projections neurons via the thalamus to the cerebral cortex. In the context of pain, the trigeminal projection to the thalamic nucleus submedius is of particular interest, as it in contrast to other spino- an trigeminothalamic projections in rats include a significant component originating in lamina I. Glutamate and aspartate immunogold labeling demonstrate that the terminals of the trigeminal projection to the nucleus submedius are enriched in glutamate but contain only low levels of aspartate. Further, the glutamate signal in these terminals, but not that of aspartate, is positively correlated with the synaptic vesicle density. Thus, glutamate is likely to serve as a neurotransmitter in trigeminothalamic tract terminals in the nucleus submedius, whereas aspartate presumably serves metabolic functions in the same terminals. A neurotransmitter role of glutamate in these terminals is also substantiated by the localization of VGLUT2 in most such terminals. VGLUT1 in the nucleus submedius is primarily located in terminals likely to originate in the ventral lateral orbital cortex. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Prof. Ulfhake, Brun, Karolinska Institute, Stockholm
organization
publishing date
type
Thesis
publication status
published
subject
keywords
neuropsykologi, neurophysiology, neuropsychology, Neurology, VGLUT2, VGLUT1, pain, somatosensory, thalamus, immunogold, glutamate, aspartate, dorsal horn, excitatory amino acids, spinal cord, neurofysiologi, Neurologi
pages
100 pages
publisher
Stefan Persson, Dept. Physiological Sciences, BMC F10, 221 84 LUND,
defense location
Segerfalkssalen
defense date
2004-05-26 10:15
ISBN
91-628-6083-6
language
English
LU publication?
yes
id
df4dd924-823f-4b3f-a071-2f80641eff32 (old id 467171)
date added to LUP
2007-09-25 14:57:41
date last changed
2016-09-19 08:45:07
@phdthesis{df4dd924-823f-4b3f-a071-2f80641eff32,
  abstract     = {The amino acid glutamate is today regarded as the main fast excitatory neurotransmitter in the central nervous system and a large body of evidence support that glutamate serves as a neurotransmitter in primary afferent terminals in the spinal cord. Previous evidence also suggests that the closely related amino acid aspartate may serve a similar role in some primary afferent terminals. However, the present quantitative analysis of aspartate immunogold labeling show that primary afferent terminals in both the superficial and deep laminae of the dorsal horn contain only low levels of aspartate. Further, whereas glutamate immunogold labeling density demonstrated a positive correlation with synaptic vesicle density in primary afferent terminals, no such correlation was evident in aspartate immunogold labeled sections. Thus, aspartate is likely to serve a metabolic role but not a neurotransmitter role in primary afferent terminals. Immunolabeling of spinal cord sections with antisera against the vesicular glutamate transporters VGLUT1 and VGLUT2 showed distribution patterns of immunolabeled varicosities consistent with an expression of mainly VGLUT2 in small caliber primary afferent fibers and of mainly VGLUT1 in large caliber primary afferent fibers. The latter suggestion was confirmed by demonstration of VGLUT1 in anterogradely labeled varicosities originating from large caliber primary afferent fibers. VGLUT1 was also detected in fibers of the corticospinal tract and in small varicosities in the spinal grey matter likely to originate from these fibers. VGLUT2 immunolabeled varicosities were distributed throughout the spinal gray matter. In addition to an origin from small caliber primary afferent fibers, such varicosities are likely to originate from intraspinal and bulbospinal neurons. The signals transmitted by primary afferent terminals are relayed through projections neurons via the thalamus to the cerebral cortex. In the context of pain, the trigeminal projection to the thalamic nucleus submedius is of particular interest, as it in contrast to other spino- an trigeminothalamic projections in rats include a significant component originating in lamina I. Glutamate and aspartate immunogold labeling demonstrate that the terminals of the trigeminal projection to the nucleus submedius are enriched in glutamate but contain only low levels of aspartate. Further, the glutamate signal in these terminals, but not that of aspartate, is positively correlated with the synaptic vesicle density. Thus, glutamate is likely to serve as a neurotransmitter in trigeminothalamic tract terminals in the nucleus submedius, whereas aspartate presumably serves metabolic functions in the same terminals. A neurotransmitter role of glutamate in these terminals is also substantiated by the localization of VGLUT2 in most such terminals. VGLUT1 in the nucleus submedius is primarily located in terminals likely to originate in the ventral lateral orbital cortex.},
  author       = {Persson, Stefan},
  isbn         = {91-628-6083-6},
  keyword      = {neuropsykologi,neurophysiology,neuropsychology,Neurology,VGLUT2,VGLUT1,pain,somatosensory,thalamus,immunogold,glutamate,aspartate,dorsal horn,excitatory amino acids,spinal cord,neurofysiologi,Neurologi},
  language     = {eng},
  pages        = {100},
  publisher    = {Stefan Persson, Dept. Physiological Sciences, BMC F10, 221 84 LUND,},
  school       = {Lund University},
  title        = {Immunocytochemical studies of excitatory amino acid neurotransmitters and transporters in the spinal cord and nucleus submedius},
  year         = {2004},
}