Molecular and electrophysiological changes in the prefrontal cortex-amygdala-dorsal periaqueductal grey pathway during persistent pain state and fear-conditioned analgesia

Ryan K. Butler, Linda Nilsson-Todd, Carine Cleren, Isabelle Léna, René Garcia, David P. Finn

Research output: Contribution to journalArticle

14 Scopus citations

Abstract

Fear-conditioned analgesia (FCA) is the reduction in pain responding which is expressed upon re-exposure to a context previously paired with an aversive stimulus. Projections along the prefrontal cortex (PFC)-amygdala-dorsal periaqueductal grey (dPAG) pathway may mediate FCA. However, there is a paucity of studies measuring both molecular and electrophysiological changes in this pathway in rats expressing persistent pain-related behaviour or FCA. Male Lister-hooded rats, with stimulating and recording electrodes implanted in the amygdala and dPAG, respectively, either received or did not receive footshock (0.4. mA) paired with context, followed 23.5. h later by an intraplantar injection of saline or formalin (50 μL, 2.5%) into the right hindpaw. Thirty minutes post-formalin/saline, rats were re-exposed to the context for 15. min, during which pain-related behaviours were assessed in addition to evoked field potential recordings in the amygdala-dPAG pathway. Immediately after the 15-minute trial, PFC tissue was isolated for measurement of total and phosphorylated extracellular-signal regulated kinase (ERK) by western blotting. Formalin-evoked nociceptive behaviour in non-fear-conditioned rats was associated with increased field potential amplitude in the dPAG and increased relative expression of phospho-ERK in the PFC. These effects were abolished in rats expressing FCA. Fear conditioning in non-formalin treated rats was associated with increased phospho-ERK in the PFC but no change in field potential amplitude in the dPAG. Together, these data suggest differential, state-dependent alterations in electrophysiological activity and ERK phosphorylation along the PFC-amygdala-dPAG pathway during pain, conditioned fear, and FCA.

Original languageEnglish (US)
Pages (from-to)1075-1081
Number of pages7
JournalPhysiology and Behavior
Volume104
Issue number5
DOIs
Publication statusPublished - Oct 24 2011
Externally publishedYes

    Fingerprint

Keywords

  • Analgesia
  • Context fear conditioning
  • Field potentials
  • Mitogen-activated protein kinase (MAPK)
  • Pain
  • Periaqueductal grey (PAG)
  • Prefrontal cortex (PFC)

ASJC Scopus subject areas

  • Experimental and Cognitive Psychology
  • Behavioral Neuroscience

Cite this