Plasticity in the link between pain-transmitting and pain-modulating systems in acute and persistent inflammation

Qiliang Chen, Mary Heinricher

Research output: Contribution to journalArticle

2 Scopus citations

Abstract

There is strong evidence that spinoparabrachial neurons in the superficial dorsal horn contribute to persistent pain states, and that the lateral parabrachial complex (PB) conveys relevant nociceptive information to higher structures. The role of PB itself in hyperalgesia and how it recruits descending facilitation has nevertheless received significantly less attention. The current study is a first step toward delineating the functional dynamics of PB and its link to descending control in acute and persistent inflammatory pain. In lightly anesthetized rats, we recorded behavioral withdrawal evoked by mechanical stimulation of the hindpaw and, simultaneously, the activity of identified pain-modulating neurons, “ON-cells” and “OFF-cells,” in the rostral ventromedial medulla (RVM). This was done before and after the inactivation of PB, contralateral or ipsilateral to an inflamed paw [1 h, 1 d, or 5– 6 d after intraplantar injection of Complete Freund’s Adjuvant (CFA)]. The inactivation of contralateral, but not ipsilateral, PB interfered with nociceptive input to RVM under basal conditions, as well as in acute inflammation. By contrast, blocking ipsilateral, but not contralateral, PB in established inflammation interfered with behavioral hyperalgesia and ON-cell and OFF-cell responses. The lesioning of contralateral PB before CFA injection prevented this recruitment of ipsilateral PB in persistent inflammation. These experiments show that contralateral PB is required to initiate hyperalgesia, which is then maintained by ipsilateral PB, most likely in both cases via the engagement of pain-modulating neurons of the RVM.

Original languageEnglish (US)
Pages (from-to)2065-2079
Number of pages15
JournalJournal of Neuroscience
Volume39
Issue number11
DOIs
StatePublished - Mar 13 2019

Keywords

  • Brainstem
  • Inflammation
  • Pain-modulation
  • Raphe
  • Rat
  • RVM

ASJC Scopus subject areas

  • Neuroscience(all)

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