Sensitization of trigeminal caudalis neuronal responses to intraoral acid and salt stimuli and desensitization by nicotine

Satoko Sudo, Makoto Sudo, Christopher T. Simons, Jean Marc Dessirier, Earl Carstens

Research output: Contribution to journalArticle

20 Scopus citations

Abstract

In human studies, repeated intraoral application of strong acidic or salt stimuli induces irritation that progressively increases across trials (sensitization), whereas irritation elicited by nicotine progressively decreases (desensitization). We investigated whether nociceptive neurons in trigeminal subnucleus caudalis (Vc) exhibit increasing or decreasing patterns of firing to the intraoral application of these irritants. In rats anesthetized with halothane and thiopental, single-unit recordings were made from nociceptive neurons in superficial layers of dorsomedial Vc that responded to mechanical and noxious thermal and chemical stimulation of the tongue. NaCl (5M), citric acid (300mM), pentanoic acid (300mM) or nicotine (600mM) were separately delivered to the tongue by constant flow (0.32ml/min) for 15 or 25min. NaCl, citric acid and pentanoic acid each elicited a progressive, significant increase in Vc neuronal firing over the initial 10min to a plateau level that was maintained for the stimulus duration. Nicotine induced a significant increase in firing rate of Vc neurons within 6min, followed by a decline back to the baseline level over the ensuing 10min. Following a rest period, reapplication of nicotine no longer activated Vc neurons, indicative of self-desensitization. We additionally tested for nicotine cross-desensitization to acid. After recording the responses of Vc neurons to pentanoic acid and noxious heat, nicotine was then applied for 15min. Post-nicotine responses to pentanoic acid were markedly reduced (to 13% of control), indicative of cross-desensitization; responses to noxious heat were also reduced to a lesser degree (to 71% of control). The progressive increase in Vc neuronal firing elicited by NaCl and acid, and the decline in firing after initial nicotinic excitation, resemble psychophysical patterns of sensitization and desensitization, respectively, and support the involvement of Vc neurons in the signaling of oral irritant sensations.

Original languageEnglish (US)
Pages (from-to)277-286
Number of pages10
JournalPain
Volume98
Issue number3
DOIs
StatePublished - 2002

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Keywords

  • Acid
  • Desensitization
  • Nicotine
  • Oral irritation
  • Salt
  • Sensitization
  • Trigeminal subnucleus caudalis

ASJC Scopus subject areas

  • Clinical Neurology
  • Psychiatry and Mental health
  • Neurology
  • Neuroscience(all)
  • Pharmacology
  • Clinical Psychology

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