Sainte-Foy-lès-Lyon, France
Sainte-Foy-lès-Lyon, France

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Coupe M.,French National Center for Scientific Research | Custaud M.-A.,French National Center for Scientific Research | Funtova I.I.,Institute of Biomedical Problems | Baevsky R.M.,Institute of Biomedical Problems | And 3 more authors.
Aviakosmicheskaya i Ekologicheskaya Meditsina | Year: 2010

After spaceflight cosmonauts often experiment orthostatic intolerance with tachycardia, hypotension and occasionally syncope In standing position. These are the results of cardiovascular deconditioning. With alterations of heart rate variability and spontaneous baroreflex sensitivity, the autonomic control of cardiovascular system is suspected to be changed by real and simulated weightlessness. However, these alterations could also reflect the changes in heart rate and in blood volume observed during spaceflights. Lower Body Negative Pressure (LBNP) was a common method used for medical checks of the cosmonauts and training for return to gravity aboard Mir space station. LBNP mimics cardiovascular orthostatic adaptation with several levels of stimulation. In this study we hypothesized that long term spaceflight alters the cardiovascular responses to LBNP. Changes of RR-interval (RRI) and systolic blood pressure (SBP) in response to LBNP were mainly observed at low level of stimulation (-25 mmHg). During stimulation by LBNP in flight, RRI tended to decrease significantly (p < 0,05) and SBP tended to increase (p < 0,05). These results emphasize the conclusion that weightlessness induces changes of sensitivity to blood volume (low pressure baroreceptors).

Mornagui B.,Laboratoire Of Physiologie Des Agressions | Rezg R.,Laboratoire Of Physiologie Des Agressions | Grissa A.,Laboratoire Of Physiologie Des Agressions | Duvareille M.,Laboratoire Of Physiologie Of Lenvironnement | And 4 more authors.
Journal of Physiology and Biochemistry | Year: 2010

Nitric oxide (NO) is a short-lived radical that functions as a neurotransmitter in the central nervous system and plays a physiological role in the regulation of hypothalamic-pituitary-adrenal axis and vasopressinergic axis. In the present study, we aimed to investigate the interaction between the generation of NO and vasopressin (AVP) and corticosterone release after 3 days of water deprivation in rats. Animals were previously treated with intraperitoneal (i.p.) saline or l-nitro-arginine methyl ester (L-NAME) injection. l-NAME is a nonspecific inhibitor of nitric oxide synthases. In control rats given i.p. saline or l-NAME, hypothalamic, pituitary, and plasma AVP levels and plasma corticosterone did not change from baseline levels (p>0.05). Three days of water deprivation increased significantly the corticosterone levels in plasma (p<0.01) and AVP levels in hypothalamus and plasma (p<0.01), but not in pituitary, which showed a significant decrease. These variations were concomitant with the elevation of nitrates/nitrates in plasma. l-NAME injection abolished significantly (p<0.01) the elevation of plasma corticosterone and hypothalamic AVP levels induced by water deprivation. These findings showed that in water-deprived rats, nitric oxide synthase inhibition by l-NAME inhibits corticosterone and vasopressin release, suggesting a potent stimulatory role of NO. © 2010 University of Navarra.

Mornagui B.,Campus University | Rezg R.,Campus University | Grissa A.,Campus University | Gharib C.,Laboratoire Of Physiologie Of Lenvironnement | And 3 more authors.
Hormone and Metabolic Research | Year: 2011

This study was performed to investigate the involvement of nitric oxide (NO) in corticosterone, endpoint product of hypothalamo-pituitary-adrenal (HPA) axis activation, and metabolic responses to 3 days of food deprivation. To investigate this aim, we used a nonspecific inhibitor of nitric oxide synthases, N-nitro-L-arginine methyl ester (L-NAME). In food deprived group we have noted a significant increase in plasma corticosterone concentration accompanied by a significant depletion in hepatic glycogen content with concomitant increase in glycogen phosphorylase (GP) activity by 63.72%, key enzyme of glycogenolysis and decrease in hexokinase (HK) activity by 25.16%, leading to significant decrease in glucose concentration. However, L-NAME administration in food deprived rats decreased slightly corticosterone level and GP activity (16.39%) and increased HK activity (11.26%) as compared to food deprived group. Considering these results, we can deduce that in food deprivation nitric oxide is involved in the regulation of corticosterone release and in glucose metabolic responses via glycogenolysis activation by the stimulation of GP activity and the inhibition of HK activity. However, more studies are necessary to further clarify the mechanisms by which NO induces these responses. © Georg Thieme Verlag KG Stuttgart - New York.

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