Reflex-related activation of putative pain facilitating neurons in rostral, ventromedial medulla requires excitatory amino acid transmission

Mary Heinricher, S. M. Roychowdhury

Research output: Contribution to journalArticle

39 Citations (Scopus)

Abstract

Although the importance of the rostral ventromedial medulla in pain modulation is generally accepted, the recognition that it can exert both pain facilitating and pain inhibiting influences, and that its constituent neuronal population is physiologically and pharmacologically heterogenous, is relatively recent. A class of neuron which may be a source of facilitating influences from the rostral ventromedial medulla has been identified in electrophysiological experiments. These neurons, termed 'on-cells,' are characterized by a sudden burst of activity beginning just before nocifensive reflexes. This burst of firing is thought to be a significant factor in brainstem control of nociceptive transmission under physiological conditions. The aim of the present study was to determine whether an excitatory amino acid is involved in generation of the reflex-related burst that defines on- cells, and more generally, to examine the role of excitatory amino acid neurotransmitters within the rostral ventromedial medulla of the rat. Iontophoretic application of the broad-spectrum excitatory amino acid receptor antagonist kynurenate significantly reduced the reflex-related on- cell burst, whereas ongoing firing was unaffected. Spontaneous activity of other medullary neurons was unchanged. These data demonstrate that release of an endogenous excitatory amino acid neurotransmitter is necessary for the activation of on-cells that is associated with nocifensive reflexes. In contrast, these receptors evidently play a much less significant role in maintaining the ongoing activity of any cell class in the rostral ventromedial medulla in lightly anaesthetized rats.

Original languageEnglish (US)
Pages (from-to)1159-1165
Number of pages7
JournalNeuroscience
Volume78
Issue number4
DOIs
StatePublished - Apr 14 1997

Fingerprint

Excitatory Amino Acids
Reflex
Neurons
Pain
Neurotransmitter Agents
Kynurenic Acid
Excitatory Amino Acid Antagonists
Glutamate Receptors
Brain Stem
Population

Keywords

  • descending control
  • iontophoresis
  • kynurenate
  • nucleus raphe magnus
  • pain modulation
  • tail flick

ASJC Scopus subject areas

  • Neuroscience(all)

Cite this

Reflex-related activation of putative pain facilitating neurons in rostral, ventromedial medulla requires excitatory amino acid transmission. / Heinricher, Mary; Roychowdhury, S. M.

In: Neuroscience, Vol. 78, No. 4, 14.04.1997, p. 1159-1165.

Research output: Contribution to journalArticle

@article{ed1c615210da48ebb236b837eae8ad07,
title = "Reflex-related activation of putative pain facilitating neurons in rostral, ventromedial medulla requires excitatory amino acid transmission",
abstract = "Although the importance of the rostral ventromedial medulla in pain modulation is generally accepted, the recognition that it can exert both pain facilitating and pain inhibiting influences, and that its constituent neuronal population is physiologically and pharmacologically heterogenous, is relatively recent. A class of neuron which may be a source of facilitating influences from the rostral ventromedial medulla has been identified in electrophysiological experiments. These neurons, termed 'on-cells,' are characterized by a sudden burst of activity beginning just before nocifensive reflexes. This burst of firing is thought to be a significant factor in brainstem control of nociceptive transmission under physiological conditions. The aim of the present study was to determine whether an excitatory amino acid is involved in generation of the reflex-related burst that defines on- cells, and more generally, to examine the role of excitatory amino acid neurotransmitters within the rostral ventromedial medulla of the rat. Iontophoretic application of the broad-spectrum excitatory amino acid receptor antagonist kynurenate significantly reduced the reflex-related on- cell burst, whereas ongoing firing was unaffected. Spontaneous activity of other medullary neurons was unchanged. These data demonstrate that release of an endogenous excitatory amino acid neurotransmitter is necessary for the activation of on-cells that is associated with nocifensive reflexes. In contrast, these receptors evidently play a much less significant role in maintaining the ongoing activity of any cell class in the rostral ventromedial medulla in lightly anaesthetized rats.",
keywords = "descending control, iontophoresis, kynurenate, nucleus raphe magnus, pain modulation, tail flick",
author = "Mary Heinricher and Roychowdhury, {S. M.}",
year = "1997",
month = "4",
day = "14",
doi = "10.1016/S0306-4522(96)00683-5",
language = "English (US)",
volume = "78",
pages = "1159--1165",
journal = "Neuroscience",
issn = "0306-4522",
publisher = "Elsevier Limited",
number = "4",

}

TY - JOUR

T1 - Reflex-related activation of putative pain facilitating neurons in rostral, ventromedial medulla requires excitatory amino acid transmission

AU - Heinricher, Mary

AU - Roychowdhury, S. M.

PY - 1997/4/14

Y1 - 1997/4/14

N2 - Although the importance of the rostral ventromedial medulla in pain modulation is generally accepted, the recognition that it can exert both pain facilitating and pain inhibiting influences, and that its constituent neuronal population is physiologically and pharmacologically heterogenous, is relatively recent. A class of neuron which may be a source of facilitating influences from the rostral ventromedial medulla has been identified in electrophysiological experiments. These neurons, termed 'on-cells,' are characterized by a sudden burst of activity beginning just before nocifensive reflexes. This burst of firing is thought to be a significant factor in brainstem control of nociceptive transmission under physiological conditions. The aim of the present study was to determine whether an excitatory amino acid is involved in generation of the reflex-related burst that defines on- cells, and more generally, to examine the role of excitatory amino acid neurotransmitters within the rostral ventromedial medulla of the rat. Iontophoretic application of the broad-spectrum excitatory amino acid receptor antagonist kynurenate significantly reduced the reflex-related on- cell burst, whereas ongoing firing was unaffected. Spontaneous activity of other medullary neurons was unchanged. These data demonstrate that release of an endogenous excitatory amino acid neurotransmitter is necessary for the activation of on-cells that is associated with nocifensive reflexes. In contrast, these receptors evidently play a much less significant role in maintaining the ongoing activity of any cell class in the rostral ventromedial medulla in lightly anaesthetized rats.

AB - Although the importance of the rostral ventromedial medulla in pain modulation is generally accepted, the recognition that it can exert both pain facilitating and pain inhibiting influences, and that its constituent neuronal population is physiologically and pharmacologically heterogenous, is relatively recent. A class of neuron which may be a source of facilitating influences from the rostral ventromedial medulla has been identified in electrophysiological experiments. These neurons, termed 'on-cells,' are characterized by a sudden burst of activity beginning just before nocifensive reflexes. This burst of firing is thought to be a significant factor in brainstem control of nociceptive transmission under physiological conditions. The aim of the present study was to determine whether an excitatory amino acid is involved in generation of the reflex-related burst that defines on- cells, and more generally, to examine the role of excitatory amino acid neurotransmitters within the rostral ventromedial medulla of the rat. Iontophoretic application of the broad-spectrum excitatory amino acid receptor antagonist kynurenate significantly reduced the reflex-related on- cell burst, whereas ongoing firing was unaffected. Spontaneous activity of other medullary neurons was unchanged. These data demonstrate that release of an endogenous excitatory amino acid neurotransmitter is necessary for the activation of on-cells that is associated with nocifensive reflexes. In contrast, these receptors evidently play a much less significant role in maintaining the ongoing activity of any cell class in the rostral ventromedial medulla in lightly anaesthetized rats.

KW - descending control

KW - iontophoresis

KW - kynurenate

KW - nucleus raphe magnus

KW - pain modulation

KW - tail flick

UR - http://www.scopus.com/inward/record.url?scp=0030918184&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0030918184&partnerID=8YFLogxK

U2 - 10.1016/S0306-4522(96)00683-5

DO - 10.1016/S0306-4522(96)00683-5

M3 - Article

C2 - 9174081

AN - SCOPUS:0030918184

VL - 78

SP - 1159

EP - 1165

JO - Neuroscience

JF - Neuroscience

SN - 0306-4522

IS - 4

ER -