title: Transport of choline out of the cranial cerebrospinal fluid spaces of the rabbit.
abstract: The role which carrier-mediated transport and passive diffusion play in the clearance of quaternary ammonium compounds from cerebrospinal fluid was evaluated by ventriculocisternal perfusion in rabbits by using [14C]choline as the primary test compound. Choline was transported out of cerebrospinal fluid by two processes: a saturable, carrier-mediated process with a Tmax of 70.5 ng/min and Kt of 2.2 microgram/min; and, a passive nonsaturable process with a cerebrospinal fluid perfusate clearance of 11.5 microliter/min. N1-methylnicotinamide depressed the clearance of choline as well as that of hexamethonium, suggesting that these cations share a common transport process. Ouabain reduced the clearance of choline and hexamethonium. Passage of choline into brain occurred by passive diffusion.
mesh_terms: D000818:Animals; D001692:Biological Transport; D002552:Cerebral Ventricles / Q000378:metabolism; D002794:Choline / Q000134:cerebrospinal fluid / Q000378:metabolism*; D006584:Hexamethonium Compounds / Q000378:metabolism; D008297:Male; D008657:Metabolic Clearance Rate; D011817:Rabbits; D012044:Regression Analysis
chemical_list: D006584:Hexamethonium Compounds; D002794:Choline