title: P2X7-related modulation of pathological nociception in rats.
abstract: Growing evidence supports a role for the immune system in the induction and maintenance of chronic pain. ATP is a key neurotransmitter in this process. Recent studies demonstrate that the glial ATP receptor, P2X7, contributes to the modulation of pathological pain. To further delineate the endogenous mechanisms that are involved in P2X7-related antinociception, we utilized a selective P2X7 receptor antagonist, A-438079, in a series of in vivo and in vitro experiments. Injection of A-438079 (10-300 micromol/kg, i.p.) was anti-allodynic in three different rat models of neuropathic pain and it attenuated formalin-induced nocifensive behaviors. Using in vivo electrophysiology, A-438079 (80 micromol/kg, i.v.) reduced noxious and innocuous evoked activity of different classes of spinal neurons (low threshold, nociceptive specific, wide dynamic range) in neuropathic rats. The effects of A-438079 on evoked firing were diminished or absent in sham rats. Spontaneous activity of all classes of spinal neurons was also significantly reduced by A-438079 in neuropathic but not sham rats. In vitro, A-438079 (1 microM) blocked agonist-induced (2,3-O-(4-benzoylbenzoyl)-ATP, 30 microM) current in non-neuronal cells taken from the vicinity of the dorsal root ganglia. Furthermore, A-438079 dose-dependently (0.3-3 microM) decreased the quantity of the cytokine, interleukin-1beta, released from peripheral macrophages. Thus, ATP, acting through the P2X7 receptor, exerts a wide-ranging influence on spinal neuronal activity following a chronic injury. Antagonism of the P2X7 receptor can in turn modulate central sensitization and produce antinociception in animal models of pathological pain. These effects are likely mediated through immuno-neural interactions that affect the release of endogenous cytokines.
authors.affiliation: Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, R4PM, AP9-1, 100 Abbott Park Road, Abbott Park, IL 60064-6118, USA. Steve.P.McGaraughty@abbott.com
authors.forename: S
authors.initials: S
authors.lastname: McGaraughty
authors.forename: K L
authors.initials: KL
authors.lastname: Chu
authors.forename: M T
authors.initials: MT
authors.lastname: Namovic
authors.forename: D L
authors.initials: DL
authors.lastname: Donnelly-Roberts
authors.forename: R R
authors.initials: RR
authors.lastname: Harris
authors.forename: X-F
authors.initials: XF
authors.lastname: Zhang
authors.forename: C-C
authors.initials: CC
authors.lastname: Shieh
authors.forename: C T
authors.initials: CT
authors.lastname: Wismer
authors.forename: C Z
authors.initials: CZ
authors.lastname: Zhu
authors.forename: D M
authors.initials: DM
authors.lastname: Gauvin
authors.forename: A C
authors.initials: AC
authors.lastname: Fabiyi
authors.forename: P
authors.initials: P
authors.lastname: Honore
authors.forename: R J
authors.initials: RJ
authors.lastname: Gregg
authors.forename: M E
authors.initials: ME
authors.lastname: Kort
authors.forename: D W
authors.initials: DW
authors.lastname: Nelson
authors.forename: W A
authors.initials: WA
authors.lastname: Carroll
authors.forename: K
authors.initials: K
authors.lastname: Marsh
authors.forename: C R
authors.initials: CR
authors.lastname: Faltynek
authors.forename: M F
authors.initials: MF
authors.lastname: Jarvis
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000700:Analgesics / Q000494:pharmacology / Q000627:therapeutic use; D000818:Animals; D001254:Astrocytoma; D001522:Behavior, Animal / Q000187:drug effects; D045744:Cell Line, Tumor; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D005727:Ganglia, Spinal; D006801:Humans; D053583:Interleukin-1beta / Q000378:metabolism; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009474:Neurons; D010147:Pain Measurement / Q000379:methods; D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D011725:Pyridines / Q000494:pharmacology* / Q000627:therapeutic use; D051381:Rats; D017207:Rats, Sprague-Dawley; D018048:Receptors, Purinergic P2 / Q000502:physiology*; D058486:Receptors, Purinergic P2X7; D012585:Sciatica / Q000188:drug therapy / Q000378:metabolism* / Q000503:physiopathology*; D013777:Tetrazoles / Q000494:pharmacology* / Q000627:therapeutic use; D013997:Time Factors
chemical_list: C523668:3-(5-(2,3-dichlorophenyl)-1H-tetrazol-1-yl)methylpyridine; D000700:Analgesics; D053583:Interleukin-1beta; C546468:P2RX7 protein, human; C546469:P2rx7 protein, mouse; C546470:P2rx7 protein, rat; D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D011725:Pyridines; D018048:Receptors, Purinergic P2; D058486:Receptors, Purinergic P2X7; D013777:Tetrazoles; C033901:3'-O-(4-benzoyl)benzoyladenosine 5'-triphosphate; D000255:Adenosine Triphosphate