title: Modulation of dural nociceptor mechanosensitivity by the nitric oxide-cyclic GMP signaling cascade.
abstract: The role of the nitric oxide (NO)-cGMP signaling cascade in modulation of peripheral nociception is controversial. Although behavioral studies have suggested both pro- and anti-nociceptive effects, little is known about the direct action of this signaling cascade on primary afferent nociceptive neurons that mediate these behaviors. Here, using single-unit recordings, we examined the direct effect of NO-cGMP signaling on spontaneous activity and mechanical responses of nociceptive afferents that innervate the dura mater. We found that the NO donor sodium nitroprusside (SNP), when applied topically to the neuronal receptive field, induced both sensitization and inhibition of the mechanical responses, albeit in different populations of neurons, which could be distinguished based on their baseline mechanical thresholds. SNP, however, did not change the level of spontaneous activity. Administration of the cGMP analogue 8-pCPT-cGMP mimicked only the inhibitory effect. When SNP was co-applied with either an inhibitor of guanylyl cyclase or a cGMP blocker, sensitization never occurred, and the inhibitory effect of SNP could also be blocked. Our findings suggest that NO can either increase or decrease the mechanical responsiveness of nociceptors and that its action might depend, in part, on the baseline level of neuronal excitability. Our results also implicate cGMP in mediating the inhibitory effect of NO.
authors.affiliation: Headache Research Laboratory, Dept. of Anesthesia and Critical Care, Beth Israel Deaconess Medical Center, Harvard Medical School, Harvard Institutes of Medicine, Room-801, 77 Avenue Louis Pasteur, Boston MA 02115, USA. dlevy1@bidmc.harvard.edu
authors.forename: Dan
authors.initials: D
authors.lastname: Levy
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Strassman
mesh_terms: D000818:Animals; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000494:pharmacology; D004338:Drug Combinations; D004388:Dura Mater / Q000502:physiology*; D004594:Electrophysiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors; D008297:Male; D008465:Mechanoreceptors / Q000502:physiology*; D009433:Neural Inhibition / Q000187:drug effects; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D009619:Nociceptors / Q000502:physiology*; D010069:Oxadiazoles / Q000494:pharmacology; D010812:Physical Stimulation; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000502:physiology*; D013873:Thionucleotides / Q000494:pharmacology
chemical_list: C095284:1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one; C090860:8-(4-chlorophenylthio)guanosine 3',5'-cyclic monophosphorothioate; D004338:Drug Combinations; D004791:Enzyme Inhibitors; D020030:Nitric Oxide Donors; D010069:Oxadiazoles; D011810:Quinoxalines; D013873:Thionucleotides; D009599:Nitroprusside; D009569:Nitric Oxide; C055656:8-((4-chlorophenyl)thio)cyclic-3',5'-GMP; D006162:Guanylate Cyclase; D006152:Cyclic GMP