open access

Vol 76, No 4 (2017)
ORIGINAL ARTICLES
Published online: 2017-05-30
Submitted: 2016-02-16
Accepted: 2016-03-14
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Neonatal exposure to monosodium glutamate results in dysmorphology of orofacial lower motor neurons

L. Foran, C. Kupelian, S. Laroia, J. Esper, R. J. Kulesza
DOI: 10.5603/FM.a2017.0052
·
Pubmed: 28612917
·
Folia Morphol 2017;76(4):582-589.

open access

Vol 76, No 4 (2017)
ORIGINAL ARTICLES
Published online: 2017-05-30
Submitted: 2016-02-16
Accepted: 2016-03-14

Abstract

Glutamate is the most abundant excitatory neurotransmitter in the central nervous system, and is stored and released by both neurons and astrocytes. Despite the important role of glutamate as a neurotransmitter, high levels of extracellular glutamate can result in excitotoxicity and apoptosis. Monosodium glutamate (MSG) is a naturally occurring sodium salt of glutamic acid that is used as a flavour enhancer in many processed foods. Neonatal exposure to MSG has been shown to result in neurodegeneration in several forebrain regions, characterised by neuronal loss and neuroendocrine abnormalities. However, the brainstem effects of neonatal MSG exposure have not been investigated. It is therefore hypothesized that MSG exposure during the early postnatal period would impact brainstem lower motor neurons involved in feeding behaviour. The effect of neonatal MSG exposure on brainstem lower motor neurons was investigated by exposing rat pups to either 4 mg/g MSG or saline from postnatal day (P) 4 through 10. On P28, brains were preserved by vascular perfusion with fixative, frozen sectioned and stained for Nïssl substance. The number, size and shape of brainstem motor neurons were compared between MSG and saline-exposed animals. MSG exposure had no impact on the total number of neurons in the nuclei examined. However, MSG exposure was associated with a significant increase in the number of round somata in both the trigeminal and facial nuclei. Furthermore, MSG exposure resulted in significantly smaller neurons in all motor nuclei examined. These results suggest that neonatal exposure to MSG impacts the development of brainstem lower motor neurons which may impact feeding and swallowing behaviours in young animals.  

Abstract

Glutamate is the most abundant excitatory neurotransmitter in the central nervous system, and is stored and released by both neurons and astrocytes. Despite the important role of glutamate as a neurotransmitter, high levels of extracellular glutamate can result in excitotoxicity and apoptosis. Monosodium glutamate (MSG) is a naturally occurring sodium salt of glutamic acid that is used as a flavour enhancer in many processed foods. Neonatal exposure to MSG has been shown to result in neurodegeneration in several forebrain regions, characterised by neuronal loss and neuroendocrine abnormalities. However, the brainstem effects of neonatal MSG exposure have not been investigated. It is therefore hypothesized that MSG exposure during the early postnatal period would impact brainstem lower motor neurons involved in feeding behaviour. The effect of neonatal MSG exposure on brainstem lower motor neurons was investigated by exposing rat pups to either 4 mg/g MSG or saline from postnatal day (P) 4 through 10. On P28, brains were preserved by vascular perfusion with fixative, frozen sectioned and stained for Nïssl substance. The number, size and shape of brainstem motor neurons were compared between MSG and saline-exposed animals. MSG exposure had no impact on the total number of neurons in the nuclei examined. However, MSG exposure was associated with a significant increase in the number of round somata in both the trigeminal and facial nuclei. Furthermore, MSG exposure resulted in significantly smaller neurons in all motor nuclei examined. These results suggest that neonatal exposure to MSG impacts the development of brainstem lower motor neurons which may impact feeding and swallowing behaviours in young animals.  

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Keywords

brainstem, facial, trigeminal, hypoglossal, vagus

About this article
Title

Neonatal exposure to monosodium glutamate results in dysmorphology of orofacial lower motor neurons

Journal

Folia Morphologica

Issue

Vol 76, No 4 (2017)

Pages

582-589

Published online

2017-05-30

DOI

10.5603/FM.a2017.0052

Pubmed

28612917

Bibliographic record

Folia Morphol 2017;76(4):582-589.

Keywords

brainstem
facial
trigeminal
hypoglossal
vagus

Authors

L. Foran
C. Kupelian
S. Laroia
J. Esper
R. J. Kulesza

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