Central regulation of autonomic functions
The major aim of the research in our group is to further study the role of the hormonal systems and body fluid composition in the integrated control of fluid balance and cardiovascular function.
|Stefan Eriksson||University lecturer, Head of Dept, joint leadership|
|Mats Rundgren||University lecturer, joint leadership|
Central and peripheral mechanisms in fluid balance and cardiovascular control
The control of body fluid composition (osmolality and ion concentrations) and body fluid volume involves several hormonal systems: vasopressin, angiotensin II, aldosterone, and atrial natriuretic peptide.
Many of these hormones influence cardiovascular function - not only by virtue of their effects on blood volume, but also through actions on endothelial cells, vascular smooth muscle, and reflex circulatory control.
Tolerance to blood loss
Local elevation (by intracerebroventricular infusion) of the cerebrospinal fluid concentration of sodium, as well as elevation of angiotensin II, has respectively been found to increase the tolerance to blood loss, and markedly affect the hemodynamic responses to blood loss in conscious sheep. The effects of sodium offer new information regarding the mechanisms of action for the so called "small volume hypertonic NaCl resuscitation" of hemorrhagic shock (blood loss).
Responses to blood poisoning
Apart from hemorrhagic shock, another "shock model" we study is septicemia (blood poisoning), where hormonal and cardiovascular responses are under characterization. One of the major cytokines, tumor necrosis factor a, has been found to be almost exclusively responsible for the "plasma leakage" during a lipopolysaccharide-induced sepsis reaction in sheep.
Substances involved in the control of food intake
A number of peptides and proteins apparently involved in the control of food intake have recently been discovered. Since a substantial part of the daily water intake is associated with eating, there are reasons to believe that these peptides and proteines may influence the control of water balance also. One such peptide, glukagon-like peptide 1, which inhibits food intake, has been found to induce negative water balance in sheep (inhibition of water intake and induction of increased urine excretion).
Work in progress aims to investigate the possible influence on fluid balance control and cardiovascular homeostasis of several other endogenous "appetite-influencing" peptides and proteins.
Most of our studies are performed in conscious sheep, surgically prepared to enable intracerebroventricular infusions, intravascular blood pressure recordings and measurements of peripheral blood flow (chronically implanted ultrasonic flow probes around the renal, femoral or mesenteric artery).
Apart from the measurements above, cardiovascular function is evaluated via a flow-directed thermodilution pulmonary arterial catheter, which allows continuous monitoring of central venous pressure, pulmonary arterial pressure, cardiac output and intermittent recordings of pulmonary capillary occlusion pressure.
Blood, urine and cerebrospinal fluid samples are routinely collected for analyses of osmolality, electrolytes and several hormones.
Hypothalamic paraventricular nucleus mediates sodium-induced changes in cardiovascular and renal function in conscious sheep.
Am. J. Physiol. Regul. Integr. Comp. Physiol. 2009 Jul;297(1):R185-93
Hyponatremia complicating labour--rare or unrecognised? A prospective observational study.
BJOG 2009 Mar;116(4):552-61
Early Achilles tendon healing in sheep.
Arch Orthop Trauma Surg 2008 Sep;128(9):1001-6
Intravenous hypertonic NaCl acts via cerebral sodium-sensitive and angiotensinergic mechanisms to improve cardiac function in haemorrhaged conscious sheep.
J. Physiol. (Lond.) 2007 Sep;583(Pt 3):1129-43
Central inhibition of opioid receptor subtypes and its effect on haemorrhagic hypotension in conscious sheep.
Acta Physiol (Oxf) 2007 Sep;191(1):25-34
Cerebral influences of sodium and angiotensin II on cardiovascular function in hypotensive hemorrhage.
Physiol. Behav. 2007 Sep;92(1-2):272-7
Low plasma volume and absent feeling of thirst--a special syndrome with a link to haemochromatosis?
J. Intern. Med. 2007 Mar;261(3):306-7