title: Protein kinase A-dependent spinal α-amino-3-hydroxy-5-methyl-4-isoxazoleproprionate-receptor trafficking mediates capsaicin-induced colon-urethra cross-organ reflex sensitization.
abstract: BACKGROUND
  Intracellular redistribution of α-amino-3-hydroxy-5-methyl-4-isoxazoleproprionate receptors (AMPARs) is known to be induced by natural painful stimulation. We tested the hypothesis that that protein kinase A (PKA)-dependent AMPAR trafficking underlies the development of N-methyl-d-aspartate receptor-mediated cross-organ sensitization in vivo.
  
  
  METHODS
  We recorded urethra reflex activity and analyzed immunoblotting of lumbosacral (L6-S2) dorsal horn (DH) tissue obtained from animal preparations after intrathecal 8-bromo-cyclic adenosine monophosphate injection or intracolonic instillation with 8-methyl-N-vanillyl-trans-6-nonenamide (capsaicin).
  
  
  RESULTS
  Intrathecal 8-bromo-cyclic adenosine monophosphate (300 μM, 10 μl) induced reflex potentiation (81.85 ± 22.21 spikes/stimulation) and increased the number of AMPAR Glu receptor 1 subunits in the membrane fraction of DH (1.8-fold increase vs. control). This process was prevented by pretreatment with the PKA inhibitor N-[2- ((p-bromocinnamyl)amino)ethyl]-5-isoquinolinesulfonamide(10 μM, 10 μl, 2.7 ± 0.8 [mean ± SE] spikes/stimulation) and human thyroid A kinase-anchoring protein (10 μM, 10 μl, 11.5 ± 4.8 spikes/stimulation), an inhibitor of PKA and PKA-A kinase-anchoring protein interactions. Intracolonic capsaicin instillation sensitized the urethra reflex (137.2 ± 62.4 spikes/stimulation) and, relative to control, simultaneously provoked an increase (2.9-fold) in the membrane fraction and a decrease (0.9-fold) in the cytosolic fraction of Glu receptor 1 subunits in DH. Inhibition of PKA activity and disruption of PKA-A kinase-anchoring protein interaction in the DH (2.0 ± 0.6 and 16.7 ± 2.8 spikes/stimulation, respectively) are sufficient to prevent capsaicin-dependent reflex sensitization and AMPAR trafficking in the membrane fraction (0.6- and 0.5-fold increase capsaicin).
  
  
  CONCLUSIONS
  Delivery of AMPAR-containing Glu receptor 1 subunits to the membranes of lumbosacral DH neurons through a PKA-dependent pathway contributes to noxious stimulation-induced synaptic strengthening, which plays roles in colon-urethra reflex sensitization.
authors.affiliation: Department of Urology, China Medical University Hospital, Taichung, Taiwan.
authors.forename: Hsien-Yu
authors.initials: HY
authors.lastname: Peng
authors.forename: Chao-Hsiang
authors.initials: CH
authors.lastname: Chang
authors.forename: Shin-Jei
authors.initials: SJ
authors.lastname: Tsai
authors.forename: Cheng-Yuan
authors.initials: CY
authors.lastname: Lai
authors.forename: Kwong-Chung
authors.initials: KC
authors.lastname: Tung
authors.forename: Hsi-Chin
authors.initials: HC
authors.lastname: Wu
authors.forename: Tzer-Bin
authors.initials: TB
authors.lastname: Lin
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D015153:Blotting, Western; D002211:Capsaicin; D003106:Colon / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D005260:Female; D051381:Rats; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000378:metabolism*; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D012018:Reflex / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018689:Sensory System Agents; D014521:Urethra / Q000378:metabolism*
chemical_list: D018091:Receptors, AMPA; D016194:Receptors, N-Methyl-D-Aspartate; D018689:Sensory System Agents; D017868:Cyclic AMP-Dependent Protein Kinases; D002211:Capsaicin