title: Transient, 5-HT2B receptor-mediated facilitation in neuropathic pain: Up-regulation of PKCγ and engagement of the NMDA receptor in dorsal horn neurons.
abstract: Spinal nociception can be facilitated by 5-HT2 receptors in neuropathic pain. We investigated the involvement of glutamate receptors in dorsal neuron hyperexcitation that is promoted by 5-HT2B receptor (5-HT2BR) after spinal nerve ligation (SNL) in the rat. Augmentation of C-fiber-evoked potentials by spinal superfusion with 5-HT2BR agonist BW 723C86 in nerve-ligated rats was impeded by co-administration of NMDA receptor (NMDAR) antagonist D-AP5, but not by mGluR1/5 antagonist AIDA or mGluR2/3 antagonist LY 341495. Evoked potentials were increased by cis-ACPD in nerve-injured rats, irrespective of simultaneous 5-HT2BR blockade by SB204741. In uninjured rats, NMDAR agonist cis-ACPD enhanced evoked potentials in the presence of BW 723C86 but not if administered alone or during exposure to protein kinase C γ (PKCγ) inhibitor peptide. Triple immunofluorescence labelings revealed co-localization of NMDAR and 5-HT2BR in PKCγ-expressing perikarya in lamina II neurons. As a result of SNL, PKCγ was transiently and bilaterally up-regulated in synaptic fraction from dorsal horn homogenates, peaking at day 2 and returning to basal levels by day 9. Chronic blockade of 5-HT2BR with selective antagonist SB 204741 after SNL bilaterally decreased the following: (i) PKCγ up-regulation in synaptic fraction, (ii) phosphorylation of NMDAR subunit NR1 (serine 889) in synaptic fraction, and (iii) co-localization of both PKCγ and phosphorylated NR1 with postsynaptic marker PSD-95. Chronic delivery of SB 204741 bilaterally attenuated thermal and mechanical allodynia occurring after SNL, particularly at day 2 post injury. These findings suggest that transient activation of the PKCγ/NMDAR pathway is critically involved in 5-HT2BR-mediated facilitation in the SNL model of neuropathic pain.
authors.affiliation: Department of Neurosciences, School of Medicine and Dentistry, University of the Basque Country, Leioa, Bizkaia, Spain Department of Neurosciences, Faculty of Pharmacy, University of the Basque Country, Vitoria-Gasteiz, Spain Department of Preventive Medicine and Public Health, School of Medicine and Dentistry, University of the Basque Country, Leioa, Bizkaia, Spain Neuroscience and Pain Research Institute, Heidelberg, Germany.
authors.forename: Zigor
authors.initials: Z
authors.lastname: Aira
authors.forename: Itsaso
authors.initials: I
authors.lastname: Buesa
authors.forename: Gontzal
authors.initials: G
authors.lastname: García Del Caño
authors.forename: Juan
authors.initials: J
authors.lastname: Bilbao
authors.forename: Francisco
authors.initials: F
authors.lastname: Doñate
authors.forename: Manfred
authors.initials: M
authors.lastname: Zimmermann
authors.forename: Jon Jatsu
authors.initials: JJ
authors.lastname: Azkue
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005071:Evoked Potentials / Q000187:drug effects; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D057809:HEK293 Cells; D006801:Humans; D006930:Hyperalgesia / Q000503:physiopathology; D007211:Indoles / Q000494:pharmacology; D008297:Male; D036421:Nerve Fibers, Unmyelinated / Q000187:drug effects / Q000502:physiology; D009437:Neuralgia / Q000378:metabolism / Q000473:pathology*; D009474:Neurons / Q000378:metabolism*; D010812:Physical Stimulation; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D044403:Receptor, Serotonin, 5-HT2B / Q000378:metabolism*; D016194:Receptors, N-Methyl-D-Aspartate; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D013126:Spinal Nerve Roots / Q000473:pathology*; D013127:Spinal Nerves; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism; D013876:Thiophenes / Q000494:pharmacology; D013997:Time Factors; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology*
chemical_list: C092430:1-(5-(2-thenyloxy)-1H-indol-3-yl)propan-2-amine; D004791:Enzyme Inhibitors; D018691:Excitatory Amino Acid Antagonists; D007211:Indoles; D044403:Receptor, Serotonin, 5-HT2B; D016194:Receptors, N-Methyl-D-Aspartate; D017366:Serotonin Receptor Agonists; D013876:Thiophenes; C087857:protein kinase C gamma; D011493:Protein Kinase C
keywords: Electrophysiology; Evoked potentials; Neuropathic pain; Serotonin; Synaptic plasticity