Effect of excitatory amino acid neurotransmitters on acid secretion in the rat stomach

Li Hsueh Tsai, Yih Jing Lee, Jang Yen Wu

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19 Citations (Scopus)

Abstract

Excitatory amino acids (EAAs), in particular, L-aspartate (L-Asp) neurons and their processes, were localized in the rat stomach using a immunohistochemical method with specific antibodies against either L-Asp or its synthesizing enzyme, aspartate aminotransferase (AAT). Myenteric ganglia and nerve bundles in the circular muscle and in the longitudinal muscle were found to be AAT-or L-Asp-positive. In addition, AAT or L-Asp-positive cells were also found in the muscle layer and the deep mucosal layer. The distribution of AAT- or L-Asp-positive cells in both the mucosal and muscle layers was heterogeneous in the stomach. In addition, L-Asp at 10-6 M negligibly influenced acid secretion in an everted preparation of isolated rat stomach. However, according to our results, L-Asp markedly inhibited the histamine-stimulated acid secretion, but not the oxotremorine- or the pentagastrin-stimulated acid secretion. Furthermore, L-Asp also inhibited histamine-induced elevation of cAMP. L-Asp itself did not affect the cAMP level although it elevated the cGMP level in the stomach. Moreover, either (+)2-amino-5-phosphonovaleric acid or (±)3-(2-carboxypiperazin-4- yl)prophyl-1-phosphonic acid, i.e. two specific antagonists for N-methyl-D- aspartic acid (NMDA) receptors, blocked the inhibitory effect of L-Asp on histamine-stimulated acid secretion or histamine-induced elevation of cAMP. Since cAMP has been strongly implicated as the second messenger involved in histamine-induced acid secretion, we believe that L-Asp regulates acid secretion in the stomach by inhibiting histamine release through the NMDA receptors, subsequently lowering the level of cAMP and ultimately reducing acid secretion.

Original languageEnglish
Pages (from-to)36-44
Number of pages9
JournalJournal of Biomedical Science
Volume6
Issue number1
Publication statusPublished - Jan 1999

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Keywords

  • Acid secretion
  • cAMP
  • cGMP
  • Excitatory amino acids
  • Histamine
  • L-Aspartic acid
  • NMDA receptor

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)

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