Ionotropic and Metabotropic Receptors, Protein Kinase A, Protein Kinase C, and Src Contribute to C-Fiber-Induced ERK Activation and cAMP Response Element-Binding Protein Phosphorylation in Dorsal Horn Neurons, Leading to Central Sensitization

Abstract

Molecular mechanisms underlying C-fiber stimulation-induced ERK (extracellular signal-regulated kinase) activation in dorsal hornneurons and its contribution to central sensitization have been investigated. In adult rat spinal slice preparations, activation of C-fiber primary afferents by a brief exposure of capsaicin produces an eightfold to 10-fold increase in ERK phosphorylation (pERK) in superficial dorsal horn neurons. The pERK induction is reduced by blockade of NMDA, AMPA/kainate, group I metabotropic glutamate receptor, neurokinin-1, and tyrosine receptor kinase receptors. The ERK activation produced by capsaicin is totally suppressed by inhibition of either protein kinase A (PKA) or PKC. PKA or PKC activators either alone or more effectively together induce pERK in superficial dorsal horn neurons. Inhibition of calcium calmodulin-dependent kinase (CaMK) has no effect, but pERK is reduced by inhibition of the tyrosine kinase Src. The induction of cAMP response element binding protein phosphorylation (pCREB) in spinal cord slices in response to C-fiber stimulation is suppressed by preventing ERK activation with the MAP kinase kinase inhibitor 2-(2-diamino-3-methoxyphenyl-4H-1-benzopyran-4-one (PD98059) and by PKA, PKC, and CaMK inhibitors. Similar signaling contributes to pERK induction after electrical stimulation of dorsal root C-fibers. Intraplantar injection of capsaicin in an intact animal increases expression of pCREB, c-Fos, and prodynorphin in the superficial dorsal horn, changes that are prevented by intrathecal injection of PD98059. Intrathecal PD98059 also attenuates capsaicin-induced secondary mechanical allodynia, a pain behavior reflecting hypersensitivity of dorsal horn neurons (central sensitization). We postulate that activation of ionotropic and metabotropic receptors by C-fiber nociceptor afferents activates ERK via both PKA and PKC, and that this contributes to central sensitization through post-translational and CREB-mediated transcriptional regulation in dorsal horn neurons.

Muscarinic receptor type 1 (M1) stimulation, probably through KCNQ/Kv7 channel closure, increases spontaneous GABA release at the dendrodendritic synapse in the mouse accessory olfactory bulb

“…To test the possibility that carbachol's action is mediated by PI3 kinase, we applied its inhibitor LY294002 (50 !M effective in slice; ) combined with the PLC inhibitor edelfosine. Carbachol application still had apparent actions under these conditions (20 !M LY294002 + 10 !M edelfosine, for more than 30 min in the holding chamber and thereafter, 100 !M LY294002 + 50 !M edelfosine for more than 15 min in the recording chamber, n = 9; direct bath 300 !M carbachol, frequencies increased by 1.1 ± 1.4 Hz) The carbachol effect was also apparent in the presence of 50 !M PD98059 (an inhibitor of MAPK pathway; the concentration reported to be effective in slices; Kawasaki et al, 2004, Yuill et al, 2007 combined with edelfosine (10 !M PD98059 + 10 !M edelfosine, for more than 50 min in the holding chamber and thereafter, 50 !M PD98059 + 50 !M edelfosine for more than 15 min in the recording chamber, n = 4; direct bath 300 !M carbachol, frequency increased by 0.0 ± 0.7 Hz).…”

Increased spinal dynorphin contributes to chronic nicotine-induced mechanical hypersensitivity in the rat

“…Paw withdrawal measurements were performed on days 5 and 14 post-osmotic pump implantation. On day 14 post-pump implantation, paw withdrawal thresholds of rats receiving 8.6 mg/kg/ day nicotine were measured at least 1 hour prior to the intrathecal administration of undiluted polyclonal anti-dynorphin A [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] antiserum (Oncogene, San Diego, CA) or normal rabbit serum (NRS). Paw withdrawal thresholds were measured by an observer blinded to treatment at 30 and 60 minutes post-dynorphin antiserum/NRS administration.…”

“…A considerable amount of evidence has accumulated to demonstrate the importance of prolonged CREB activation in central sensitization [21] and a number of pain-related genes are upregulated by pCREB including the immediate early gene c-fos [16], brain-derived neurotrophic factor (BDNF) [4], calcitonin gene-related peptide (CGRP) [8], the neurokinin 1 receptor [2], and prodynorphin [16].…”

Bradykinin Enhances AMPA and NMDA Receptor Activity in Spinal Cord Dorsal Horn Neurons by Activating Multiple Kinases to Produce Pain Hypersensitivity

“…These include glutamate itself acting on NMDA, mGluR, and AMPA receptors; substance P acting on NK1 receptors; BDNF acting on TrkB receptors; and PGE 2 acting on EP receptors (Ji et al, 2003). These ligand-gated ion channels, GPCRs, and receptor tyrosine kinases activate intracellular signaling pathways in dorsal horn neurons that include PKC, CaM kinase, Src, and ERK, to increase synaptic efficacy and produce homosynaptic and heterosynaptic facilitation (Ji et al, 1999(Ji et al, , 2003Kawasaki et al, 2004).…”