Effect of neonatal treatment with monosodium glutamate on dopaminergic and L-DOPA-ergic neurons of the medial basal hypothalamus and on prolactin and MSH secretion of rats

I. Bodnár, Pál Göõz, Hitoshi Okamura, B. Tóth, M. Vecsernyés, B. Halász, György M. Nagy

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Abstract

The effect of neonatal treatment with monosodium L-glutamate (MSG) on the dopaminergic systems of the medial basal hypothalamus has been investigated using tyrosine hydroxylase (TH) and aromatic L-amino acid decarboxylase (AADC) immunocytochemistry. Changes in plasma levels of prolactin (PRL) and α-melanocyte-stimulating hormone (MSH) have also been determined in intact and in MSG-treated rats after inhibition of TH by α-methyl-p-tyrosine (α-MpT) or without inhibition of enzyme activity. Monosodium glutamate resulted in a 40% reduction in the number of TH immunopositive tuberoinfundibular neurons, but no change in the number of AADC-positive tuberoinfundibular nerve cells, indicating that this reduction has occurred mainly in TH-positive but AADC-negative elements, i.e., in L-DOPA-ergic neurons. In contrast, MSG did not cause changes in the number of TH and AADC immunoreactive neurons of the periventriculohypophysial and tuberohypophysial dopaminergic systems, and it did not influence basal plasma PRL levels. α-methyl-p-tyrosine has increased plasma PRL concentrations in both control and MSG-treated rats of both sexes, but significantly higher responses were detected in females. None of the treatments had any effect on plasma MSH level. These findings suggest that MSG affects primarily L-DOPA-ergic neurons located in the ventrolateral part of the arcuate nucleus, but not dopaminergic neurons situated in the dorsomedial part of the arcuate nucleus; neither PRL nor MSH secretion is altered by MSG; a significant sex difference exists in the pituitary PRL response to inhibition of TH, and this response is not affected by MSG.

Original languageEnglish
Pages (from-to)767-774
Number of pages8
JournalBrain Research Bulletin
Volume55
Issue number6
DOIs
Publication statusPublished - 2001

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Middle Hypothalamus
Melanocyte-Stimulating Hormones
Sodium Glutamate
Prolactin
Tyrosine 3-Monooxygenase
Glutamic Acid
Neurons
Carboxy-Lyases
Arcuate Nucleus of Hypothalamus
Therapeutics
Amino Acids
Tyrosine
Aromatic-L-Amino-Acid Decarboxylases
Dopaminergic Neurons
Sex Characteristics
Immunohistochemistry

Keywords

  • Arcuate nucleus
  • Aromatic L-amino acid decarboxylase
  • Immunocytochemistry
  • Tyrosine hydroxylase

ASJC Scopus subject areas

  • Neuroscience(all)

Cite this

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title = "Effect of neonatal treatment with monosodium glutamate on dopaminergic and L-DOPA-ergic neurons of the medial basal hypothalamus and on prolactin and MSH secretion of rats",
abstract = "The effect of neonatal treatment with monosodium L-glutamate (MSG) on the dopaminergic systems of the medial basal hypothalamus has been investigated using tyrosine hydroxylase (TH) and aromatic L-amino acid decarboxylase (AADC) immunocytochemistry. Changes in plasma levels of prolactin (PRL) and α-melanocyte-stimulating hormone (MSH) have also been determined in intact and in MSG-treated rats after inhibition of TH by α-methyl-p-tyrosine (α-MpT) or without inhibition of enzyme activity. Monosodium glutamate resulted in a 40{\%} reduction in the number of TH immunopositive tuberoinfundibular neurons, but no change in the number of AADC-positive tuberoinfundibular nerve cells, indicating that this reduction has occurred mainly in TH-positive but AADC-negative elements, i.e., in L-DOPA-ergic neurons. In contrast, MSG did not cause changes in the number of TH and AADC immunoreactive neurons of the periventriculohypophysial and tuberohypophysial dopaminergic systems, and it did not influence basal plasma PRL levels. α-methyl-p-tyrosine has increased plasma PRL concentrations in both control and MSG-treated rats of both sexes, but significantly higher responses were detected in females. None of the treatments had any effect on plasma MSH level. These findings suggest that MSG affects primarily L-DOPA-ergic neurons located in the ventrolateral part of the arcuate nucleus, but not dopaminergic neurons situated in the dorsomedial part of the arcuate nucleus; neither PRL nor MSH secretion is altered by MSG; a significant sex difference exists in the pituitary PRL response to inhibition of TH, and this response is not affected by MSG.",
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author = "I. Bodn{\'a}r and P{\'a}l G{\"o}{\~o}z and Hitoshi Okamura and B. T{\'o}th and M. Vecserny{\'e}s and B. Hal{\'a}sz and Nagy, {Gy{\"o}rgy M.}",
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T1 - Effect of neonatal treatment with monosodium glutamate on dopaminergic and L-DOPA-ergic neurons of the medial basal hypothalamus and on prolactin and MSH secretion of rats

AU - Bodnár, I.

AU - Göõz, Pál

AU - Okamura, Hitoshi

AU - Tóth, B.

AU - Vecsernyés, M.

AU - Halász, B.

AU - Nagy, György M.

PY - 2001

Y1 - 2001

N2 - The effect of neonatal treatment with monosodium L-glutamate (MSG) on the dopaminergic systems of the medial basal hypothalamus has been investigated using tyrosine hydroxylase (TH) and aromatic L-amino acid decarboxylase (AADC) immunocytochemistry. Changes in plasma levels of prolactin (PRL) and α-melanocyte-stimulating hormone (MSH) have also been determined in intact and in MSG-treated rats after inhibition of TH by α-methyl-p-tyrosine (α-MpT) or without inhibition of enzyme activity. Monosodium glutamate resulted in a 40% reduction in the number of TH immunopositive tuberoinfundibular neurons, but no change in the number of AADC-positive tuberoinfundibular nerve cells, indicating that this reduction has occurred mainly in TH-positive but AADC-negative elements, i.e., in L-DOPA-ergic neurons. In contrast, MSG did not cause changes in the number of TH and AADC immunoreactive neurons of the periventriculohypophysial and tuberohypophysial dopaminergic systems, and it did not influence basal plasma PRL levels. α-methyl-p-tyrosine has increased plasma PRL concentrations in both control and MSG-treated rats of both sexes, but significantly higher responses were detected in females. None of the treatments had any effect on plasma MSH level. These findings suggest that MSG affects primarily L-DOPA-ergic neurons located in the ventrolateral part of the arcuate nucleus, but not dopaminergic neurons situated in the dorsomedial part of the arcuate nucleus; neither PRL nor MSH secretion is altered by MSG; a significant sex difference exists in the pituitary PRL response to inhibition of TH, and this response is not affected by MSG.

AB - The effect of neonatal treatment with monosodium L-glutamate (MSG) on the dopaminergic systems of the medial basal hypothalamus has been investigated using tyrosine hydroxylase (TH) and aromatic L-amino acid decarboxylase (AADC) immunocytochemistry. Changes in plasma levels of prolactin (PRL) and α-melanocyte-stimulating hormone (MSH) have also been determined in intact and in MSG-treated rats after inhibition of TH by α-methyl-p-tyrosine (α-MpT) or without inhibition of enzyme activity. Monosodium glutamate resulted in a 40% reduction in the number of TH immunopositive tuberoinfundibular neurons, but no change in the number of AADC-positive tuberoinfundibular nerve cells, indicating that this reduction has occurred mainly in TH-positive but AADC-negative elements, i.e., in L-DOPA-ergic neurons. In contrast, MSG did not cause changes in the number of TH and AADC immunoreactive neurons of the periventriculohypophysial and tuberohypophysial dopaminergic systems, and it did not influence basal plasma PRL levels. α-methyl-p-tyrosine has increased plasma PRL concentrations in both control and MSG-treated rats of both sexes, but significantly higher responses were detected in females. None of the treatments had any effect on plasma MSH level. These findings suggest that MSG affects primarily L-DOPA-ergic neurons located in the ventrolateral part of the arcuate nucleus, but not dopaminergic neurons situated in the dorsomedial part of the arcuate nucleus; neither PRL nor MSH secretion is altered by MSG; a significant sex difference exists in the pituitary PRL response to inhibition of TH, and this response is not affected by MSG.

KW - Arcuate nucleus

KW - Aromatic L-amino acid decarboxylase

KW - Immunocytochemistry

KW - Tyrosine hydroxylase

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DO - 10.1016/S0361-9230(01)00584-6

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EP - 774

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JF - Brain Research Bulletin

SN - 0361-9230

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