title: D2-like receptor activation does not initiate a brain docosahexaenoic acid signal in unanesthetized rats.
abstract: BACKGROUND
  The polyunsaturated fatty acid, docosahexaenoic acid (DHA), participates in neurotransmission involving activation of calcium-independent phospholipase A2 (iPLA2), which is coupled to muscarinic, cholinergic and serotonergic neuroreceptors. Drug induced activation of iPLA2 can be measured in vivo with quantitative autoradiography using 14C-DHA as a probe. The present study used this approach to address whether a DHA signal is produced following dompaminergic (D)2-like receptor activation with quinpirole in rat brain. Unanesthetized rats were infused intravenously with 14C-DHA one minute after saline or quinpirole infusion, and serial blood samples were collected over a 20-minute period to obtain plasma. The animals were euthanized with sodium pentobarbital and their brains excised, coronally dissected and subjected to quantitative autoradiography to derive the regional incorporation coefficient, k*, a marker of DHA signaling. Plasma labeled and unlabeled unesterified DHA concentrations were measured.
  
  
  RESULTS
  The incorporation coefficient (k*) for DHA did not differ significantly between quinpirole-treated and control rats in any of 81 identified brain regions. Plasma labeled DHA concentration over the 20-minute collection period (input function) and unlabeled unesterified DHA concentration did not differ significantly between the two groups.
  
  
  CONCLUSIONS
  These findings demonstrate that D2-like receptor initiated signaling does not involve DHA as a second messenger, and likely does not involve iPLA2 activation.
authors.affiliation: Brain Physiology and Metabolism Section, Laboratory of Neuroscience, National Institute on Aging, National Institutes of Health, Bldg, 9, Room 1S126, Bethesda, MD 20892, USA. ameer.taha@gmail.com.
authors.forename: Ameer Y
authors.initials: AY
authors.lastname: Taha
authors.forename: Lisa
authors.initials: L
authors.lastname: Chang
authors.forename: Mei
authors.initials: M
authors.lastname: Chen
authors.forename: Stanley I
authors.initials: SI
authors.lastname: Rapoport
authors.forename: Epolia
authors.initials: E
authors.lastname: Ramadan
mesh_terms: D000818:Animals; D001345:Autoradiography; D001774:Blood Chemical Analysis; D001921:Brain / Q000187:drug effects* / Q000378:metabolism*; D002250:Carbon Radioisotopes; D004281:Docosahexaenoic Acids / Q000378:metabolism*; D018491:Dopamine Agonists / Q000494:pharmacology*; D005227:Fatty Acids / Q000097:blood; D008297:Male; D019257:Quinpirole / Q000494:pharmacology*; D011897:Random Allocation; D011916:Rats, Inbred F344; D017448:Receptors, Dopamine D2 / Q000819:agonists / Q000378:metabolism
chemical_list: D002250:Carbon Radioisotopes; D018491:Dopamine Agonists; D005227:Fatty Acids; D017448:Receptors, Dopamine D2; D019257:Quinpirole; D004281:Docosahexaenoic Acids