P2X2 receptor immunoreactivity in the dorsal vagal complex and area postrema of the rat

L. Atkinson, T. F C Batten, J. Deuchars

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47 Citations (Scopus)

Abstract

Adenosine 5'-triphosphate (ATP) can function as a fast synaptic transmitter through its actions on ionotropic (P2X) and metabotropic (P2Y) receptors in neuronal tissue. The ionotropic receptors have been classified into seven subtypes (P2X1-P2X7) by molecular cloning. However, they are difficult to distinguish pharmacologically owing to an absence of specific agonists and antagonists. In this study we used neuroanatomical methods to determine the origin and neurochemical phenotype of the P2X2 subtype of purinoceptor in the dorsal medulla of the rat. Using immunohistochemistry we observed dense networks of P2X2 receptor immunoreactive labelled fibres and terminals in the dorsal vagal complex and area postrema, as well as labelled cell bodies in the dorsal vagal nucleus and the area postrema. The P2X2 receptor was localized presynaptically in vagal afferent fibres and terminals in the nucleus tractus solitarius at the ultrastructural level by combining injections of an anterograde tracer (biotin dextran amine) into the nodose ganglion with pre-embedding immunogold visualization of P2X2 immunoreactivity. Terminals immunoreactive for the P2X2 receptor in the nucleus tractus solitarius were found to contain glutamate, but not GABA immunoreactivity by post-embedding immunogold-labelling techniques. In cell bodies in the area postrema, dual immunofluorescence also indicated that P2X2 receptor immunoreactive cells are glutamatergic but not GABAergic. The P2X2 receptor was localized to vagal preganglionic neurons in the dorsal vagal nucleus that were identified by prior intraperitoneal injections of the retrograde tracer FluoroGold. No cells immunoreactive for the P2X2 receptor were observed in the nucleus tractus solitarius. The localization of P2X2 receptor immunoreactivity presynaptically in vagal afferent terminals indicates that the receptor may be involved in modulating transmitter release from vagal afferent fibres. Furthermore, the presence of the P2X2 receptor in vagal preganglionic cells and in glutamatergic cells of the area postrema implies that it may, respectively, play a role in regulation of vagal efferent cell activity and modulation of excitatory outputs from the area postrema to other brain regions. (C) 2000 IBRO.
Original languageEnglish
Pages (from-to)683-696
Number of pages14
JournalNeuroscience
Volume99
Issue number4
DOIs
Publication statusPublished - 23 Aug 2000
Externally publishedYes

Keywords

  • Dorsal vagal motor nucleus
  • Nucleus tractus solitarius
  • P2X receptor
  • Vagal afferent fibres

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