title: Cerebral hemodynamics and brain oxygen changes related to gravity-induced loss of consciousness in rhesus monkeys.
abstract: The aim of the present experiment was to study the influence of +Gz acceleration (head-to-foot inertial forces) onset on cerebral oxygenation changes (cerebral oxy- and deoxy-hemoglobin) and cerebral blood volume (CBV) in order to evaluate the role of cerebral hypoxemia and ischemia in the appearance of +Gz-induced loss of consciousness (G-LOC). We used five rhesus monkeys which were equipped with near infrared spectroscopy optodes fixed onto the parietooccipital cranial bone. G-LOC (isoelectric electrocorticogram) was detected with silver balls electrodes in contact with the dura matter. The animals were centrifuged up to +12 Gz with two onset rates (0.1 and 3 G/s). Cerebral deoxy-hemoglobin increased significantly (max: +30 +/- 6% of control, P < 0.01) only during the 0.1 G/s run. At G-LOC, CBV changes were not related to G-onset rate (P = 0.30; mean change: -32 +/- 6% of control). We conclude that cerebral ischemia is the main mechanism in the occurrence of G-LOC.
authors.affiliation: Institut de Médecine Aérospatiale du Service de Santé des Armées, Département Physiologie, BP 73, 91223 Brétigny-sur-Orge Cedex, France. dtran@imassa.fr
authors.forename: Cong Chi
authors.initials: CC
authors.lastname: Tran
authors.forename: Geneviève
authors.initials: G
authors.lastname: Florence
authors.forename: Eric
authors.initials: E
authors.lastname: Tinet
authors.forename: Didier
authors.initials: D
authors.lastname: Lagarde
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Bouy
authors.forename: Pascal
authors.initials: P
authors.lastname: Van Beers
authors.forename: André
authors.initials: A
authors.lastname: Serra
authors.forename: Sigrid
authors.initials: S
authors.lastname: Avrillier
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Ollivier
mesh_terms: D000054:Acceleration / Q000009:adverse effects; D000818:Animals; D001921:Brain / Q000502:physiology*; D018470:Gravity, Altered / Q000009:adverse effects*; D006439:Hemodynamics / Q000502:physiology; D008253:Macaca mulatta; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D010108:Oxyhemoglobins / Q000502:physiology; D014474:Unconsciousness / Q000378:metabolism
chemical_list: D010108:Oxyhemoglobins