| 1. |
- Eriksson, S, et al.
(författare)
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Hypertension and thirst outlasting renal vasoconstriction as effects of a brief evaluation of systemic angiotensin II in sheep.
- 1994
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Ingår i: Acta Physiologica Scandinavica. - : Wiley. - 0001-6772 .- 1365-201X. ; 150:2, s. 181-8
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Tidskriftsartikel (refereegranskat)abstract
- The influence of 10 min intracarotid (i.c.) and intravenous (i.v.) infusions of angiotensin II (Ang II; 20 pmol kg-1 min-1) on carotid blood pressure (cBP) and renal blood flow (RBF) was studied in unanaesthetized ewes without and with pre-treatment with the alpha 1- and beta-adrenoceptor blocker labetalol. RBF was also monitored during 30 min intracerebroventricular (ICV) infusions of Ang II at 2 pmol kg-1 min-1. The i.c. infusions of Ang II induced about 50 mmHg rise in cBP. A steep decline occurred during 5 min post-infusion, followed by a much slower reduction with the cBP remaining above control level at 40 min post-infusion. The pressure elevation induced by i.v. Ang II was less pronounced but exhibited a similar pattern. Labetalol significantly reduced the pressor response to i.c. as well as i.v. Ang II. The i.c. and i.v. infusions of Ang II conspicuously reduced the RBF regardless of whether the ewes were labetalol-treated or not. At 5 min after the infusions RBF had returned to control level. The ICV infusions did not influence the RBF. Ang II i.c. elicited thirst in 50% of the ewes with the urge to drink remaining at 40 min post-infusion. The dipsogenic response was not reduced by labetalol pretreatment. The results imply that no cerebral component contributes to the reduction in RBF induced by systemic Ang II. However, a centrally mediated action seems to be the cause of the long-lasting post-infusion cBP elevation and dipsogenic response.(ABSTRACT TRUNCATED AT 250 WORDS)
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| 2. |
- Gunnarsson, Ulf, 1967-, et al.
(författare)
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Centrally mediated influences of hypertonic NaCl and angiotensin II on regional blood flow and hemodynamic responses to hypotensive hemorrhage in conscious sheep.
- 1994
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Ingår i: Shock. - 1073-2322 .- 1540-0514. ; 2:1, s. 60-7
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Tidskriftsartikel (refereegranskat)abstract
- The influence of separate and combined intracerebroventricular (ICV) infusions of hypertonic (.5 M) NaCl (HTNa) at .02 mL min-1 and angiotensin II (ANG II) at 1 pmol kg-1 min-1 on tolerance to hemorrhage, accompanying systemic hemodynamic changes, and regional blood flow was studied in adult conscious sheep. Corresponding measurements during ICV .9% NaCl served as controls. The hemorrhage volume needed to lower the blood pressure to about 50 mmHg was significantly larger during treatment with HTNa and HTNa/ANG II (27.8 +/- 2.2 and 28.3 +/- 2.5 mL kg-1, respectively; p < .001; about 45% of estimated blood volume) as well as during ANG II (20.1 +/- 1.3 mL kg-1; p < .01) compared to controls (15.1 +/- .7 mL kg-1; about 25% of estimated blood volume). In spite of a larger hemorrhage volume, the lowering of the cardiac output was not accentuated, and its subsequent recovery was not impaired during ICV infusion of HTNa or HTNa/ANG II. Similarly, the posthemorrhage restoration of the systemic blood pressure was not negatively affected by the more pronounced hypovolemia induced during the ICV treatments compared to controls. In contrast to ANG II, HTNa infusion, alone or in combination with ANG II, was accompanied by a significantly lower renal blood flow, and a higher renovascular resistance, during the posthemorrhage period. The femoral blood flow was maintained or even slightly elevated after hemorrhage in all experiments. The integrated results of the study imply differentiated hemodynamic effects of centrally administered HTNa and ANG II.(ABSTRACT TRUNCATED AT 250 WORDS)
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| 3. |
- Gunnarsson, Ulf, 1967-, et al.
(författare)
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Inefficiency of intracerebroventricular ANP to alter haemodynamic, plasma vasopressin and renin responses to haemorrhage in sheep.
- 1994
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Ingår i: Acta Physiologica Scandinavica. - : Wiley. - 0001-6772 .- 1365-201X. ; 150:4, s. 441-7
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Tidskriftsartikel (refereegranskat)abstract
- Whether intracerebroventricular (i.c.v.) infusion of atrial natriuretic peptide (human-ANP, 1-28) 25 pmol min-1 influences the tolerance to blood loss and haemorrhage induced cardiovascular, vasopressin and renin responses were studied in five conscious sheep. The i.c.v. infusion was started 60 min prior to a slow (0.7 ml kg-1 min-1) venous haemorrhage, was run concurrently with bleeding, and for 90 min thereafter. Venous blood was removed until the mean systemic arterial pressure suddenly fell to about 50 mmHg. There were no statistically significant differences in either the bleeding volume necessary to induce the sudden decrease in blood pressure, or in cardiovascular parameters measured by venous heart thermodilution catheterization, compared with control experiments with i.c.v. infusion of artificial CSF. The plasma protein and vasopressin concentrations and renin activity were unaffected by the i.c.v. infusion of ANP as were the changes in these parameters occurring during the subsequent haemorrhage. The same negative findings were obtained with a three times higher dose of ANP(1-28) (75 pmol min-1), tested in three of the animals. Thus the i.c.v. infusion of ANP(1-28), in amounts expected to elevate the CSF concentration far above basal levels does apparently not influence normal blood pressure regulation or alter haemodynamic, vasopressin and renin responses to haemorrhage in conscious sheep.
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| 4. |
- Gunnarsson, Ulf, 1967-
(författare)
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Intracerebroventricular ANP(1-28) has no obvious effects on renal blood flow and function in conscious sheep.
- 1994
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Ingår i: Clinical and experimental pharmacology & physiology. - 0305-1870 .- 1440-1681. ; 21:3, s. 189-94
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Tidskriftsartikel (refereegranskat)abstract
- 1. The study examines whether intracerebroventricular (ICV) infusion of atrial natriuretic peptide (human ANP,1-28) influences renal electrolyte and water excretion, vasopressin release, renal and femoral blood flows in conscious ewes. The blood flow was measured by chronically implanted ultrasonic flow probes. 2. ICV infusion of ANP(1-28) at 25 pmol/min for 60 min did not affect renal Na and K excretion or plasma vasopressin levels. In two out of six animals a mild water diuresis developed at about 50 min post-infusion. 3. The plasma osmolality, Na, K and protein concentrations did not change during the experiments. 4. The renal and femoral arterial blood flows were not influenced by 30 min ICV infusions of ANP(1-28) at 25 and 85 pmol/min. 5. It is concluded that human ANP(1-28) has no, or negligible, effects on renal function, femoral and renal blood flow when given ICV in amounts obviously elevating cerebrospinal fluid levels far above normal.
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| 5. |
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| 6. |
- Hjelmqvist, H, et al.
(författare)
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Increased resistance to haemorrhage induced by intracerebroventricular infusion of hypertonic NaCl in conscious sheep.
- 1992
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Ingår i: Acta Physiologica Scandinavica. - : Wiley. - 0001-6772 .- 1365-201X. ; 145:2, s. 177-86
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Tidskriftsartikel (refereegranskat)abstract
- The effect of elevated cerebrospinal fluid Na+ concentration (CSF [Na+]) on the tolerance of blood loss, and concomitant cardiovascular and humoral responses were studied in conscious sheep. A slow (0.7 ml kg-1 min-1) venous haemorrhage was continued until the mean systemic arterial pressure suddenly decreased to less than 50 mmHg, or in the absence of hypotension, until a total blood loss of 25 ml kg-1. Significantly more blood had to be removed to induce hypotension in animals receiving an intracerebroventricular (i.c.v.) infusion (0.02 ml min-1) of 0.5 M NaCl (starting 30 min before haemorrhage and continued throughout the experiment) compared to control haemorrhages without concomitant i.c.v. infusion (22.7 +/- 1.2 ml vs 16.9 +/- 0.9 ml kg-1). In one animal, subjected to 0.5 M NaCl infusion, the blood pressure was still maintained at 25 ml kg-1 of haemorrhage. In spite of a larger blood loss, animals receiving i.c.v. infusion of hypertonic NaCl had an improved recovery of the blood pressure after haemorrhage, due to a better maintained cardiac output rather than to a reinforced increase of the vascular resistance. The improved cardiovascular responses to haemorrhage during elevated CSF [Na+] are not readily explained by the effects on the plasma concentrations of vasopressin, angiotensin II or noradrenaline, although the latter was augmented. The plasma protein concentration decreased already during the 30 min of hypertonic NaCl infusion preceding haemorrhage, and the haemodilution caused by the subsequent blood removal was aggravated, which indicates that this treatment also causes transfer of fluid to the plasma compartment. We conclude that elevated CSF [Na+] increases tolerance to haemorrhage and improves cardiovascular function after blood loss in sheep. Since the haemodynamic responses in many respects were similar to those reported in response to the systemic administration of a small volume of hypertonic NaCl solution in haemorrhagic shock, part of the effect of that treatment may be mediated via cerebral effects of increased Na+ concentration.
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| 7. |
- Rundgren, M, et al.
(författare)
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Intracerebroventricular infusion of glycine stimulates vasopressin release in conscious sheep.
- 1993
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Ingår i: NeuroReport. - 0959-4965 .- 1473-558X. ; 4:8, s. 1052-4
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Tidskriftsartikel (refereegranskat)abstract
- We have previously observed that elevation of the plasma glycine concentration stimulates vasopressin (AVP) release in man and sheep. In the present study we show that this effect of glycine can be elicited directly via a cerebral site of action in conscious sheep. Intracerebroventricular infusions of 0.05 and 0.15 M glycine solutions increased the plasma AVP concentration by 6 and 50 times, respectively, while no effect on water intake was observed. Hyperhydration did not block the stimulation of AVP release. No behavioural side effects, or changes in blood pressure, were observed in response to the infusions.
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