Spinally projecting preproglucagon axons preferentially innervate sympathetic preganglionic neurons
File(s)
Published version
Author(s)
Type
Journal Article
Abstract
Glucagon-like peptide-1 (GLP-1) affects central autonomic neurons, including those controlling the cardiovascular system, thermogenesis, and energy balance. Preproglucagon (PPG) neurons, located mainly in the nucleus tractus solitarius (NTS) and medullary reticular formation, produce GLP-1. In transgenic mice expressing glucagon promoter-driven yellow fluorescent protein (YFP), these brainstem PPG neurons project to many central autonomic regions where GLP-1 receptors are expressed. The spinal cord also contains GLP-1 receptor mRNA but the distribution of spinal PPG axons is unknown.
Here, we used two-color immunoperoxidase labeling to examine PPG innervation of spinal segments T1–S4 in YFP-PPG mice. Immunoreactivity for YFP identified spinal PPG axons and perikarya. We classified spinal neurons receiving PPG input by immunoreactivity for choline acetyltransferase (ChAT), nitric oxide synthase (NOS) and/or Fluorogold (FG) retrogradely transported from the peritoneal cavity. FG microinjected at T9 defined cell bodies that supplied spinal PPG innervation.
The deep dorsal horn of lower lumbar cord contained YFP-immunoreactive neurons. Non-varicose, YFP-immunoreactive axons were prominent in the lateral funiculus, ventral white commissure and around the ventral median fissure. In T1–L2, varicose, YFP-containing axons closely apposed many ChAT-immunoreactive sympathetic preganglionic neurons (SPN) in the intermediolateral cell column (IML) and dorsal lamina X. In the sacral parasympathetic nucleus, about 10% of ChAT-immunoreactive preganglionic neurons received YFP appositions, as did occasional ChAT-positive motor neurons throughout the rostrocaudal extent of the ventral horn. YFP appositions also occurred on NOS-immunoreactive spinal interneurons and on spinal YFP-immunoreactive neurons. Injecting FG at T9 retrogradely labeled many YFP-PPG cell bodies in the medulla but none of the spinal YFP-immunoreactive neurons.
These results show that brainstem PPG neurons innervate spinal autonomic and somatic motor neurons. The distributions of spinal PPG axons and spinal GLP-1 receptors correlate well. SPN receive the densest PPG innervation. Brainstem PPG neurons could directly modulate sympathetic outflow through their spinal inputs to SPN or interneurons.
Here, we used two-color immunoperoxidase labeling to examine PPG innervation of spinal segments T1–S4 in YFP-PPG mice. Immunoreactivity for YFP identified spinal PPG axons and perikarya. We classified spinal neurons receiving PPG input by immunoreactivity for choline acetyltransferase (ChAT), nitric oxide synthase (NOS) and/or Fluorogold (FG) retrogradely transported from the peritoneal cavity. FG microinjected at T9 defined cell bodies that supplied spinal PPG innervation.
The deep dorsal horn of lower lumbar cord contained YFP-immunoreactive neurons. Non-varicose, YFP-immunoreactive axons were prominent in the lateral funiculus, ventral white commissure and around the ventral median fissure. In T1–L2, varicose, YFP-containing axons closely apposed many ChAT-immunoreactive sympathetic preganglionic neurons (SPN) in the intermediolateral cell column (IML) and dorsal lamina X. In the sacral parasympathetic nucleus, about 10% of ChAT-immunoreactive preganglionic neurons received YFP appositions, as did occasional ChAT-positive motor neurons throughout the rostrocaudal extent of the ventral horn. YFP appositions also occurred on NOS-immunoreactive spinal interneurons and on spinal YFP-immunoreactive neurons. Injecting FG at T9 retrogradely labeled many YFP-PPG cell bodies in the medulla but none of the spinal YFP-immunoreactive neurons.
These results show that brainstem PPG neurons innervate spinal autonomic and somatic motor neurons. The distributions of spinal PPG axons and spinal GLP-1 receptors correlate well. SPN receive the densest PPG innervation. Brainstem PPG neurons could directly modulate sympathetic outflow through their spinal inputs to SPN or interneurons.
Date Issued
2014-11-01
Date Acceptance
2014-10-24
Citation
Neuroscience, 2014, 284, pp.872-887
ISSN
0306-4522
Publisher
Elsevier
Start Page
872
End Page
887
Journal / Book Title
Neuroscience
Volume
284
Copyright Statement
This is an open access article under the
CC BY license (http://creativecommons.org/licenses/by/3.0/).
CC BY license (http://creativecommons.org/licenses/by/3.0/).
License URL
Sponsor
Medical Research Council (MRC)
Grant Number
MR/J013293/1
Subjects
Science & Technology
Life Sciences & Biomedicine
Neurosciences
Neurosciences & Neurology
choline acetyltransferase
green fluorescent protein
glucagon-like peptide-1
nucleus of the solitary tract
parasympathetic preganglionic neurons
retrograde tracing
GLUCAGON-LIKE PEPTIDE-1
AMPHETAMINE-REGULATED TRANSCRIPT
CENTRAL-NERVOUS-SYSTEM
NITRIC-OXIDE SYNTHASE
BROWN ADIPOSE-TISSUE
BRAIN-STEM
RECEPTOR STIMULATION
FOOD-INTAKE
HEART-RATE
GASTROINTESTINAL-TRACT
Adrenergic Fibers
Animals
Axons
Bacterial Proteins
Choline O-Acetyltransferase
Female
Glucagon-Like Peptide-1 Receptor
Immunoenzyme Techniques
Interneurons
Luminescent Proteins
Male
Medulla Oblongata
Mice, Transgenic
Motor Neurons
Neuroanatomical Tract-Tracing Techniques
Nitric Oxide Synthase
Peritoneal Cavity
Posterior Horn Cells
Proglucagon
Sacrum
Stilbamidines
Thoracic Vertebrae
Neurology & Neurosurgery
1109 Neurosciences
1701 Psychology
Publication Status
Published