title: Nitric oxide suppresses L-type calcium currents in basilar artery smooth muscle cells in rabbits.
abstract: OBJECTIVE
  Nitric oxide (NO) is well known to be a vasodilator, and NO donor compounds are currently used for treating vasospasm following subarachnoid hemorrhage. However, the action mechanism of cerebral vascular relaxation is not yet clear. L-type calcium channels have been determined to play an essential role in smooth muscle contraction. To investigate the role of L-type calcium channels in NO-induced relaxation of basilar smooth muscle cells, we examined the effect of the NO donor, sodium nitroprusside (SNP) on calcium (Ca2+) currents using smooth muscle cells isolated from a rabbit basilar artery.
  
  
  METHODS
  The smooth muscle cells were isolated from rabbit basilar artery by enzyme treatment. To identify L-type Ca2+ currents, we used cesium chloride, a potassium channel blocker and Bay K8644, an activator of L-type Ca2+ channel.
  
  
  RESULTS
  The L-type calcium currents (91±13.0 pA; n = 11) were significantly reduced by SNP (32±5 pA; n = 11; P<0.05). 1H-[1,2,4] Oxadiazolo [4,3-a] quinoxalin-1-one, a 3',5'-cyclic guanosine monophosphate inhibitor, blocked the effect of SNP on L-type Ca2+ currents, and similar results were obtained after the application of 7-nitroindazole, a specific NO synthase inhibitor. Furthermore, inward currents were enhanced by Bay K8644 (170±22 pA; n = 5) and were suppressed by SNP (54±13 pA; n = 5; P<0.05).
  
  
  CONCLUSIONS
  These results demonstrate that NO suppresses the L-type Ca2+ currents in rabbit basilar smooth muscle cells, and suggest that L-type Ca2+ channels may play a pivotal role in NO-induced vascular relaxation.
authors.affiliation: Department of Pediatrics & Research Institute of Clinical Medicine, School of Medicine, Chonbuk National University, Jeonju, Korea.
authors.forename: Naveen
authors.initials: N
authors.lastname: Sharma
authors.forename: Janardhan Prasad
authors.initials: JP
authors.lastname: Bhattarai
authors.forename: Pyoung Han
authors.initials: PH
authors.lastname: Hwang
authors.forename: Seong Kyu
authors.initials: SK
authors.lastname: Han
mesh_terms: D000818:Animals; D001488:Basilar Artery / Q000187:drug effects / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers / Q000494:pharmacology; D011817:Rabbits; D014664:Vasodilation / Q000502:physiology*; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D020746:Calcium Channels, L-Type; D020030:Nitric Oxide Donors; D026902:Potassium Channel Blockers; D014665:Vasodilator Agents; D009599:Nitroprusside; D009569:Nitric Oxide