title: Transmitters and pathways mediating inhibition of spinal itch-signaling neurons by scratching and other counterstimuli.
abstract: Scratching relieves itch, but the underlying neural mechanisms are poorly understood. We presently investigated a role for the inhibitory neurotransmitters GABA and glycine in scratch-evoked inhibition of spinal itch-signaling neurons in a mouse model of chronic dry skin itch. Superficial dorsal horn neurons ipsilateral to hindpaw dry skin treatment exhibited a high level of spontaneous firing that was significantly attenuated by cutaneous scratching, pinch and noxious heat. Scratch-evoked inhibition was nearly abolished by spinal delivery of the glycine antagonist, strychnine, and was markedly attenuated by respective GABA(A) and GABA(B) antagonists bicuculline and saclofen. Scratch-evoked inhibition was also significantly attenuated (but not abolished) by interruption of the upper cervical spinal cord, indicating the involvement of both segmental and suprasegmental circuits that engage glycine- and GABA-mediated inhibition of spinal itch-signaling neurons by noxious counterstimuli.
authors.affiliation: Department of Neurobiology, Physiology and Behavior, University of California Davis, Davis, California, United States of America.
authors.forename: Tasuku
authors.initials: T
authors.lastname: Akiyama
authors.forename: Mirela
authors.initials: M
authors.lastname: Iodi Carstens
authors.forename: Earl
authors.initials: E
authors.lastname: Carstens
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002574:Cervical Vertebrae / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D018756:GABA Antagonists / Q000494:pharmacology; D005998:Glycine / Q000037:antagonists & inhibitors / Q000378:metabolism; D051379:Mice; D008813:Mice, Inbred ICR; D008959:Models, Neurological; D009407:Nerve Block; D009433:Neural Inhibition / Q000187:drug effects; D009434:Neural Pathways / Q000187:drug effects / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D018377:Neurotransmitter Agents / Q000378:metabolism*; D010812:Physical Stimulation; D011537:Pruritus / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology; D015398:Signal Transduction / Q000187:drug effects; D013127:Spinal Nerves / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology*; D013331:Strychnine / Q000494:pharmacology; D013696:Temperature
chemical_list: D018756:GABA Antagonists; D018377:Neurotransmitter Agents; D013331:Strychnine; D005998:Glycine