title: Acetylcholine stimulates the release of nitric oxide from rat spinal cord.
abstract: BACKGROUND
  Acetylcholine causes synthesis of nitric oxide in vascular endothelium, and presumptive evidence in vivo suggests spinally released acetylcholine causes antinociception and increased sympathetic nervous system activity via a nitric oxide mechanism. The purpose of this study was to determine, using a recently described bioassay system, whether acetylcholine stimulates nitric oxide release from spinal cord tissue in vitro.
  
  
  METHODS
  Rat thoracolumbar spinal cord slices were incubated in a tissue chamber and perfused with Krebs-Henseleit solution. The perfusate was then passed through endotheliumdenuded rat aortic rings and their tension was measured. Vascular rings were preconstricted with phenylephrine, then were exposed to spinal cord perfusate with increasing concentrations (10(-12)-10(-4)M) of acetylcholine alone or with various antagonists.
  
  
  RESULTS
  Acetylcholine perfusion of spinal tissue caused concentration-dependent relaxations of the aortic rings, an effect blocked by each of the muscarinic antagonists, atropine, pirenzepine, and AFDX-116. Acetylcholine-induced relaxation also was antagonized by an inhibitor of nitric oxide synthase (N-methyl-L-arginine), a nitric oxide scavenger (hemoglobin) and an inhibitor of guanylate cyclase (methylene blue).
  
  
  CONCLUSIONS
  These results demonstrate release of a vasorelaxant from spinal cord tissue by acetylcholine, which results from an action on muscarinic receptors and exhibits a pharmacology consistent with nitric oxide. Although precise anatomic localization of acetylcholine's action is not possible with this system, these results add to evidence that acetylcholine causes nitric oxide synthesis in the spinal cord.
authors.affiliation: Department of Anesthesia, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, North Carolina 27157-1009, USA.
authors.forename: Z
authors.initials: Z
authors.lastname: Xu
authors.forename: C
authors.initials: C
authors.lastname: Tong
authors.forename: J C
authors.initials: JC
authors.lastname: Eisenach
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D008297:Male; D009569:Nitric Oxide / Q000096:biosynthesis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000187:drug effects* / Q000378:metabolism; D014664:Vasodilation / Q000187:drug effects
chemical_list: D009569:Nitric Oxide; D000109:Acetylcholine