Influence of nitric oxide synthase inhibition on vasopressin and corticosterone secretion during water deprivation in rats.

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.

Blood volume measurement: The comparison of pulse dye densitometry and Dill and Costill's methods.

In many clinical situations, it is crucial to determine circulating blood volume (BV) easily and to repeat this measurement. The Dye DensitoGram Analyzer (DDG, Nihon Kohden Corp) measures semi-automatically BV, using an injection of IndoCyanine Green (ICG, 10 mg), and avoiding intermittent blood samples. The DDG was used during a 90-day microgravity simulation by Head-Down-Tilt bed rest (HDT) to measure BV and compared with the calculation of the plasma volume (PV) variations according to Dill and Costill's formula (DC).

Does resistance exercise prevent body fluid changes after a 90-day bed rest?

Although various exercise regimens are commonly used as countermeasures to reduce the cardiovascular deconditioning induced by microgravity, the underlying mechanisms are not well understood. In this study we aimed to test whether lower limb resistance exercise with flywheel technology can prevent the fluid homeostasis alterations induced by 90-day head-down tilt bed-rest (HDT), and thus improve orthostatic tolerance. Total body water (TBW, measured by isotope dilution) and plasma volume (PV, calculated from the haemoglobin and the haematocrit) were measured in a control group (Co, n=9) and a countermeasure group (CM, n=9).

Orthostatic tolerance and spontaneous baroreflex sensitivity in men versus women after 7 days of head-down bed rest.

Many factors are involved in the development of orthostatic intolerance after real or simulated weightlessness. The aim of our study was to compare the effects of 7-day head-down bed rest (HDBR) in eight women and eight men on the spontaneous baroreflex sensitivity (standard spectral method and new time-frequency algorithm) during lower body negative pressure (LBNP) tests. Results obtained before HDBR have shown in women, compared to men, higher heart rate, lower blood pressure, higher parasympathetic modulation at rest and greater decrease in baroreflex sensitivity with greater increase in sympathetic activity during LBNP.