title: Na concentration of CSF and cardiovascular adjustment in thermally dehydrated rats.
abstract: To assess the effect of the Na concentration of cerebrospinal fluid (CSF) on arterial pressure regulation under dehydration, the Na concentration in CSF ([Na]csf) was measured continuously with an Na-sensitive electrode in the lateral ventricle (LV) together with mean arterial pressure (MAP), central venous pressure (CVP) and cardiac output (CO) during and after hypotonic infusion (INF, approximately 200 mOsm/kg H2O, 5 microliters/min for 10 min) into the LV of dehydrated and pentobarbital anesthetized rats. Total vascular conductance (TVC) was calculated from CO/(MAP-CVP). Sino-aortic denervation was performed to eliminate any influence of arterial baroreflexes on MAP changed by [Na]csf. After dehydration, MAP increased by 20 mmHg (p < 0.001) despite a 9% decrease in blood volume (p < 0.001) while [Na]csf increased by 13 mEq/kg H2O (p < 0.001). This increase in MAP was attributed to the decrease in TVC. After hypotonic INF began, MAP and [Na]csf decreased and the maximal decreases of -13 mmHg (p < 0.001) and -28 mEq/kg H2O (p < 0.001) were found at the end of INF, respectively. The changes in MAP (r = 0.97, p < 0.001), CO (r = 0.97, p < 0.001), and TVC (r = -0.90, p < 0.001) were highly correlated with the change in [Na]csf during INF and the following 10-min recovery. These results suggest that the increase in [Na]csf is involved in the maintenance of arterial pressure by decreasing TVC and by attenuating the decrease in CO caused by dehydration-induced hypovolemia.
authors: Department of Physiology, Kyoto Prefectural University of Medicine, Japan.
authors: M
authors: M
authors: Chen
mesh_terms: D000315:Adrenalectomy; D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D002415:Cats; D005260:Female; D008297:Male; D051381:Rats; D012018:Reflex / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000502:physiology*; D013997:Time Factors; D001743:Urinary Bladder / Q000502:physiology*; D014661:Vasoconstriction / Q000502:physiology*; D017833:Visceral Afferents / Q000502:physiology*