Cerebral cortical blood flow in rabbits during parabolic flights (hypergravity and microgravity) |
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Authors: | Geneviève Florence Marc Lemenn Sylvain Desert Fran?ois Bourron André Serra Richard Bonnier Jean-Pierre Blanquie Robert Charbonné and Jacques Seylaz |
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Institution: | (1) Institut de Médecine Aérospatiale du Service de Santé des Armées, Département de Physiologie Gravitationnelle, BP 73, F-91 223 Brétigny sur Orge Cedex, France, FR;(2) Bio Pharm Technology, Centre d'Etudes du Mousseau, F-41 150 Mesland, France, FR;(3) Laboratoire de Recherches Cérébrovasculaires, Centre National de la Recherche Scientifique Unité Anociée 641, Université Paris VII, 10 avenue de Verdun, F-75 010 Paris, France, FR |
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Abstract: | We studied the effect of gravity on cerebral cortical blood flow (CBF), mean arterial blood pressure () and heart rate in six rabbits exposed to parabolic flights. The CBF was obtained using a laser-Doppler probe fixed on to
a cranial window. Before weightlessness, the animals were exposed to chest-to-back directed acceleration (1.8–2.0 g). The CBF values were expressed as a percentage of CBFo (mean CBF during 60 s before the 1st parabola). Propranolol (1 mg · kg−1 IV) was given after the 11th parabola and pentobarbital (12–15 mg · kg−1 IV) after the 16th parabola. Before the administration of the drugs, CBF increased (P < 0.01) during hypergravity i.e. maximal CBF 151 (SD 64)% CBFo. Simultaneously increased maximal , 119 (SD 11) mmHg (P < 0.01)]. At the onset of weightlessness, CBF and reached maximal values 194 (SD 96)% CBFo (P < 0.01) and 127 (SD 19) mmHg, (P < 0.01) respectively]. The microgravity-induced increase in CBF was transient since CBF returned to its baseline value after
8 (SD 2) s of microgravity. After propranolol administration, CBF was not statistically different during hypergravity but
an elevation of CBF was still observed in weightlessness. The increases in CBF and also persisted during weightlessness after pentobarbital administration. These data would indicate that CBF of nonanesthetized
rabbits increases during the first seconds of weightlessness and demonstrate the involvement of rapid active regulatory mechanisms
since CBF returned to control values within 8 (SD 2) s. We concluded that this elevation in blood flow was not related to
stress because it persisted after the administration of propranolol and pentobarbital.
Accepted: 6 November 1997 |
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Keywords: | Cerebral circulation Weightlessness Laser-Doppler flowmetry |
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