title: Imaging signal transduction via arachidonic acid in the human brain during visual stimulation, by means of positron emission tomography.
abstract: BACKGROUND
  Arachidonic acid (AA, 20:4n-6), an important second messenger, is released from membrane phospholipid following receptor mediated activation of phospholipase A(2) (PLA(2)). This signaling process can be imaged in brain as a regional brain AA incorporation coefficient K*.
  
  
  OBJECTIVE
  K* will be increased in brain visual areas of subjects submitted to visual stimulation.
  
  
  METHODS
  Regional values of K* were measured with positron emission tomography (PET), following the intravenous injection of [1-(11)C]AA, in 16 healthy volunteers subjected to visual stimulation at flash frequencies 2.9 Hz (8 subjects) or 7.8 Hz (8 subjects), compared with the dark (0 Hz) condition. Regional cerebral blood flow (rCBF) was measured with intravenous [(15)O]water under comparable conditions.
  
  
  RESULTS
  During flash stimulation at 2.9 Hz or 7.8 Hz vs. 0 Hz, K* was increased significantly by 2.3-8.9% in Brodmann areas 17, 18 and 19, and in additional frontal, parietal and temporal cortical regions. rCBF was increased significantly by 3.1-22%, often in comparable regions. Increments at 7.8 Hz often exceeded those at 2.9 Hz for both K* and rCBF. Decrements in both parameters also were produced, particularly in frontal brain regions.
  
  
  CONCLUSIONS
  AA plays a role in signaling processes provoked by visual stimulation, since visual stimulation at flash frequencies of 2.9 and 7.8 Hz compared to 0 Hz modifies both K* for AA and rCBF in visual and related areas of the human brain. The two-stimulus condition paradigm of this study might be used with PET to image effects of other functional activations and of drugs on brain signaling via AA.
authors.affiliation: Brain Physiology and Metabolism Section, Bldg. 9, Rm. 1S128, National Institute on Aging, National Institutes of Health, 9 Memorial Drive, Bethesda, MD 20892, USA.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Esposito
authors.forename: Giampiero
authors.initials: G
authors.lastname: Giovacchini
authors.forename: Margaret
authors.initials: M
authors.lastname: Der
authors.forename: Jeih-San
authors.initials: JS
authors.lastname: Liow
authors.forename: Abesh K
authors.initials: AK
authors.lastname: Bhattacharjee
authors.forename: Kaizong
authors.initials: K
authors.lastname: Ma
authors.forename: Peter
authors.initials: P
authors.lastname: Herscovitch
authors.forename: Michael
authors.initials: M
authors.lastname: Channing
authors.forename: William C
authors.initials: WC
authors.lastname: Eckelman
authors.forename: Mark
authors.initials: M
authors.lastname: Hallett
authors.forename: Richard E
authors.initials: RE
authors.lastname: Carson
authors.forename: Stanley I
authors.initials: SI
authors.lastname: Rapoport
mesh_terms: D000328:Adult; D016718:Arachidonic Acid / Q000502:physiology*; D001921:Brain / Q000000981:diagnostic imaging* / Q000502:physiology; D002250:Carbon Radioisotopes; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D010741:Phospholipases A / Q000378:metabolism; D010775:Photic Stimulation; D049268:Positron-Emission Tomography / Q000379:methods*; D011859:Radiography; D015290:Second Messenger Systems; D015398:Signal Transduction
chemical_list: D002250:Carbon Radioisotopes; D016718:Arachidonic Acid; D010741:Phospholipases A