Cellular relations between μ-opioid receptive, GABAergic and reticulospinal neurons in the rostral ventrolateral medulla

Teresa A. Milner, Carrie T. Drake, Sue Aicher

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Physiological studies have suggested that μ-opioid receptor (MOR) activation can both excite and inhibit reticulospinal neurons in the rostral ventrolateral medulla (RVL), possibly via influences on GABAergic neurons. Thus, to determine the cellular relationships of MORs to GABAergic neurons in the RVL, two experimental approaches were used. First, single sections through the RVL were labeled for MOR using immunoperoxidase detection and for GABA using immunogold detection and examined by electron microscopy. These studies revealed that MOR-immunoreactive (IR) terminals were smaller on average than GABA-IR terminals and formed both asymmetric and symmetric synapses, whereas GABA-IR terminals formed exclusively symmetric synapses. MOR and GABA immunoreactivities rarely co-localized. Interactions between axons and terminals containing MOR or GABA immunoreactivity were primarily: (1) direct appositions with each other; or (2) convergence onto a common dendritic target that sometimes contained either MOR or GABA immunoreactivity. Since the identity of these target dendrites mostly was unknown, a second study was designed to determine if they might be reticulospinal neurons. For this study, reticulospinal neurons were identified with a retrograde tracer and both MOR and GABA were localized in the same sections of the RVL. These studies revealed that numerous GABA-IR terminals formed symmetric synapses on the perikarya and proximal dendrites of reticulospinal neurons. In contrast, few MOR-IR terminals contacted reticulospinal perikarya and large dendrites although they were often found nearby. These results provide anatomical evidence that MOR activation by endogenous or exogenous agonists may indirectly alter GABAergic neurotransmission in the RVL either through presynaptic interactions between cells or through competing influences on postsynaptic targets.

Original languageEnglish (US)
Pages (from-to)1-14
Number of pages14
JournalBrain Research
Volume917
Issue number1
DOIs
StatePublished - Oct 26 2001

Fingerprint

GABAergic Neurons
gamma-Aminobutyric Acid
Opioid Analgesics
Dendrites
Synapses
Neurons
Presynaptic Terminals
Opioid Receptors
Cell Communication
Synaptic Transmission
Electron Microscopy

Keywords

  • C1 adrenergic area
  • Electron microscopy
  • Enkephalin
  • Ultrastructure

ASJC Scopus subject areas

  • Neuroscience(all)

Cite this

Cellular relations between μ-opioid receptive, GABAergic and reticulospinal neurons in the rostral ventrolateral medulla. / Milner, Teresa A.; Drake, Carrie T.; Aicher, Sue.

In: Brain Research, Vol. 917, No. 1, 26.10.2001, p. 1-14.

Research output: Contribution to journalArticle

@article{0f14e15941da4e6aa88ed5be9ad818e4,
title = "Cellular relations between μ-opioid receptive, GABAergic and reticulospinal neurons in the rostral ventrolateral medulla",
abstract = "Physiological studies have suggested that μ-opioid receptor (MOR) activation can both excite and inhibit reticulospinal neurons in the rostral ventrolateral medulla (RVL), possibly via influences on GABAergic neurons. Thus, to determine the cellular relationships of MORs to GABAergic neurons in the RVL, two experimental approaches were used. First, single sections through the RVL were labeled for MOR using immunoperoxidase detection and for GABA using immunogold detection and examined by electron microscopy. These studies revealed that MOR-immunoreactive (IR) terminals were smaller on average than GABA-IR terminals and formed both asymmetric and symmetric synapses, whereas GABA-IR terminals formed exclusively symmetric synapses. MOR and GABA immunoreactivities rarely co-localized. Interactions between axons and terminals containing MOR or GABA immunoreactivity were primarily: (1) direct appositions with each other; or (2) convergence onto a common dendritic target that sometimes contained either MOR or GABA immunoreactivity. Since the identity of these target dendrites mostly was unknown, a second study was designed to determine if they might be reticulospinal neurons. For this study, reticulospinal neurons were identified with a retrograde tracer and both MOR and GABA were localized in the same sections of the RVL. These studies revealed that numerous GABA-IR terminals formed symmetric synapses on the perikarya and proximal dendrites of reticulospinal neurons. In contrast, few MOR-IR terminals contacted reticulospinal perikarya and large dendrites although they were often found nearby. These results provide anatomical evidence that MOR activation by endogenous or exogenous agonists may indirectly alter GABAergic neurotransmission in the RVL either through presynaptic interactions between cells or through competing influences on postsynaptic targets.",
keywords = "C1 adrenergic area, Electron microscopy, Enkephalin, Ultrastructure",
author = "Milner, {Teresa A.} and Drake, {Carrie T.} and Sue Aicher",
year = "2001",
month = "10",
day = "26",
doi = "10.1016/S0006-8993(01)02827-X",
language = "English (US)",
volume = "917",
pages = "1--14",
journal = "Brain Research",
issn = "0006-8993",
publisher = "Elsevier",
number = "1",

}

TY - JOUR

T1 - Cellular relations between μ-opioid receptive, GABAergic and reticulospinal neurons in the rostral ventrolateral medulla

AU - Milner, Teresa A.

AU - Drake, Carrie T.

AU - Aicher, Sue

PY - 2001/10/26

Y1 - 2001/10/26

N2 - Physiological studies have suggested that μ-opioid receptor (MOR) activation can both excite and inhibit reticulospinal neurons in the rostral ventrolateral medulla (RVL), possibly via influences on GABAergic neurons. Thus, to determine the cellular relationships of MORs to GABAergic neurons in the RVL, two experimental approaches were used. First, single sections through the RVL were labeled for MOR using immunoperoxidase detection and for GABA using immunogold detection and examined by electron microscopy. These studies revealed that MOR-immunoreactive (IR) terminals were smaller on average than GABA-IR terminals and formed both asymmetric and symmetric synapses, whereas GABA-IR terminals formed exclusively symmetric synapses. MOR and GABA immunoreactivities rarely co-localized. Interactions between axons and terminals containing MOR or GABA immunoreactivity were primarily: (1) direct appositions with each other; or (2) convergence onto a common dendritic target that sometimes contained either MOR or GABA immunoreactivity. Since the identity of these target dendrites mostly was unknown, a second study was designed to determine if they might be reticulospinal neurons. For this study, reticulospinal neurons were identified with a retrograde tracer and both MOR and GABA were localized in the same sections of the RVL. These studies revealed that numerous GABA-IR terminals formed symmetric synapses on the perikarya and proximal dendrites of reticulospinal neurons. In contrast, few MOR-IR terminals contacted reticulospinal perikarya and large dendrites although they were often found nearby. These results provide anatomical evidence that MOR activation by endogenous or exogenous agonists may indirectly alter GABAergic neurotransmission in the RVL either through presynaptic interactions between cells or through competing influences on postsynaptic targets.

AB - Physiological studies have suggested that μ-opioid receptor (MOR) activation can both excite and inhibit reticulospinal neurons in the rostral ventrolateral medulla (RVL), possibly via influences on GABAergic neurons. Thus, to determine the cellular relationships of MORs to GABAergic neurons in the RVL, two experimental approaches were used. First, single sections through the RVL were labeled for MOR using immunoperoxidase detection and for GABA using immunogold detection and examined by electron microscopy. These studies revealed that MOR-immunoreactive (IR) terminals were smaller on average than GABA-IR terminals and formed both asymmetric and symmetric synapses, whereas GABA-IR terminals formed exclusively symmetric synapses. MOR and GABA immunoreactivities rarely co-localized. Interactions between axons and terminals containing MOR or GABA immunoreactivity were primarily: (1) direct appositions with each other; or (2) convergence onto a common dendritic target that sometimes contained either MOR or GABA immunoreactivity. Since the identity of these target dendrites mostly was unknown, a second study was designed to determine if they might be reticulospinal neurons. For this study, reticulospinal neurons were identified with a retrograde tracer and both MOR and GABA were localized in the same sections of the RVL. These studies revealed that numerous GABA-IR terminals formed symmetric synapses on the perikarya and proximal dendrites of reticulospinal neurons. In contrast, few MOR-IR terminals contacted reticulospinal perikarya and large dendrites although they were often found nearby. These results provide anatomical evidence that MOR activation by endogenous or exogenous agonists may indirectly alter GABAergic neurotransmission in the RVL either through presynaptic interactions between cells or through competing influences on postsynaptic targets.

KW - C1 adrenergic area

KW - Electron microscopy

KW - Enkephalin

KW - Ultrastructure

UR - http://www.scopus.com/inward/record.url?scp=0035955481&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0035955481&partnerID=8YFLogxK

U2 - 10.1016/S0006-8993(01)02827-X

DO - 10.1016/S0006-8993(01)02827-X

M3 - Article

C2 - 11602225

AN - SCOPUS:0035955481

VL - 917

SP - 1

EP - 14

JO - Brain Research

JF - Brain Research

SN - 0006-8993

IS - 1

ER -