Role of neuronal nicotinic-acetylcholine receptors in the activation of neurons in trigeminal subnucleus caudalis by nicotine delivered to the oral mucosa

Earl Carstens, Christopher T. Simons, Jean Marc Dessirier, M. Iodi Carstens, Steven L. Jinks

Research output: Contribution to journalArticle

20 Scopus citations

Abstract

To characterize the role of neuronal nicotinic acetylcholine receptors (nAChRs) in oral irritation and pain, we employed the method of c-fos immunohistochemistry to map the locations and numbers of brainstem neurons that express the immediate-early gene, c-fos, after application of nicotine to the tongue, either alone or after pretreatment with cholinergic antagonists. Groups of anesthetized rats received the following chemicals delivered bilaterally to the dorsal tongue: (1) 0.9% NaCl followed by nicotine (1%, 61 mM), (2) the nAChR antagonist, mecamylamine 0.1% (= 4.9 mM) followed by nicotine, (3) the muscarinic antagonist atropine (0.1%, 1.46 mM) followed by nicotine, (4) atropine (1%, 14.6 mM) followed by nicotine, (5) 0.9% NaCl as a control, and (6) unstimulated controls. Two hours later, animals were perfused with phosphate-buffered saline followed by 4% paraformaldehyde through the aorta. Postfixed brainstems were cut in 50-μm frozen sections and immunohistochemically processed for fos-like immunoreactivity (FLI). Following application of nicotine, there were significant increases in FLI compared with saline-treated controls in dorsomedial and ventrolateral aspects of the trigeminal caudalis. Pretreatment with either mecamylamine or the high (1%) concentration of atropine significantly reduced nicotine-evoked FLI in these areas, while pretreatment with the low (0.1%) atropine concentration did not significantly affect FLI. These results are consistent with the idea that nicotine activates nAChRs residing on lingual nociceptive fibers, which, in turn, excite neurons in trigeminal caudalis.

Original languageEnglish (US)
Pages (from-to)375-383
Number of pages9
JournalExperimental Brain Research
Volume132
Issue number3
StatePublished - 2000

Keywords

  • c-fos
  • Irritation
  • Neuronal nicotinic acetylcholine receptor
  • Pain
  • Trigeminal caudalis

ASJC Scopus subject areas

  • Neuroscience(all)

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