title: Targeted increase in cerebral blood flow by transcranial near-infrared laser irradiation.
abstract: OBJECTIVE
  Brain function is highly dependent on cerebral blood flow (CBF). The precise mechanisms by which blood flow is controlled by NIR laser irradiation on the central nervous system (CNS) have not been elucidated. In this study, we examined the effect of 808 nm laser diode irradiation on CBF in mice.
  
  
  METHODS
  We examined the effect of NIR irradiation on CBF at three different power densities (0.8, 1.6 and 3.2 W/cm(2)) and directly measured nitric oxide (NO) in brain tissue during NIR laser irradiation using an amperometric NO-selective electrode. We also examined the contribution of NO and a neurotransmitter, glutamate, to the regulation of CBF by using a nitric oxide synthase (NOS) inhibitor, N(g)-nitro-L-arginine methyl ester hydrochloride (L-NAME), and an N-methyl-D-aspartate (NMDA) receptor blocker, MK-801, respectively. We examined the change in brain tissue temperature during NIR laser irradiation. We also investigated the protection effect of NIR laser irradiation on transient cerebral ischemia using transient bilateral common carotid artery occlusion (BCCAO) in mice.
  
  
  RESULTS
  We showed that NIR laser irradiation (1.6 W/cm(2) for 15-45 minutes) increased local CBF by 30% compared to that in control mice. NIR laser irradiation also induced a significant increase in cerebral NO concentration. In mice that received L-NAME, NIR laser irradiation did not induce any increase in CBF. Mice administered MK-801 showed an immediate increase but did not show a delayed additional increase in local CBF. The increase in brain tissue temperature induced by laser irradiation was estimated to be as low as 0.8 degrees C at 1.6 W/cm(2), indicating that the heating effect is not a main mechanism of the CBF increase in this condition. Pretreatment with NIR laser irradiation improved residual CBF and reduced the numbers of apoptotic cells in the hippocampus.
  
  
  CONCLUSIONS
  Our data suggest that NIR laser irradiation is a promising experimental and therapeutic tool in the field of cerebral circulation research.
authors.affiliation: Department of Neurosurgery, National Defense Medical College, 3-2 Namiki, Tokorozawa, Saitama 359-8513, Japan.
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Uozumi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nawashiro
authors.forename: Shunichi
authors.initials: S
authors.lastname: Sato
authors.forename: Satoko
authors.initials: S
authors.lastname: Kawauchi
authors.forename: Katsuji
authors.initials: K
authors.lastname: Shima
authors.forename: Makoto
authors.initials: M
authors.lastname: Kikuchi
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000528:radiation effects; D001831:Body Temperature / Q000528:radiation effects; D001921:Brain / Q000378:metabolism* / Q000473:pathology / Q000528:radiation effects; D002545:Brain Ischemia / Q000517:prevention & control; D016893:Carotid Stenosis / Q000150:complications; D002560:Cerebrovascular Circulation / Q000528:radiation effects*; D016291:Dizocilpine Maleate / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007834:Lasers; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D018696:Neuroprotective Agents / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D011829:Radiation Dosage
chemical_list: D004791:Enzyme Inhibitors; D018696:Neuroprotective Agents; D009569:Nitric Oxide; D016291:Dizocilpine Maleate; D019331:NG-Nitroarginine Methyl Ester