title: Diurnal variation of cerebral blood flow in rat hippocampus.
abstract: We measured local cerebral blood flow over 24 hours in 10 unanesthetized, freely moving rats to determine whether blood flow in the hippocampus fluctuated as a function of time of day. We measured hydrogen clearance at 1-hour intervals using a polyurethane-coated platinum electrode with a 1-mm bare tip implanted in the dorsal hippocampus. Individual rats displayed a wide range of local cerebral blood flow values (from 30 to 100 ml/min/100 g tissue) in a day. In seven of the 10 rats, the overall mean hippocampal blood flow for the dark cycle (7 PM-5 AM) was significantly (p less than 0.001, 0.01, or 0.05) greater than that for the light cycle (6 AM-6 PM), showing an average increase of 20%. Further, the maximum mean hippocampal blood flow at 11 PM in all 10 rats was 42% greater than the minimum at noon. Our study demonstrates for the first time that local cerebral blood flow in the hippocampus shows diurnal variation.
authors.affiliation: Department of Physiology, Yokohama City University School of Medicine, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Endo
authors.forename: K
authors.initials: K
authors.lastname: Jinnai
authors.forename: M
authors.initials: M
authors.lastname: Endo
authors.forename: K
authors.initials: K
authors.lastname: Fujita
authors.forename: F
authors.initials: F
authors.lastname: Kimura
mesh_terms: D000818:Animals; D002940:Circadian Rhythm; D003624:Darkness; D006624:Hippocampus / Q000098:blood supply*; D008027:Light; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values; D012039:Regional Blood Flow