Effect of intraventricular injection of transmitter substances and temperature on autonomic functions of conscious sheep.

Abstract

SUMMARY1. Changes in cardiovascular and renal functions following injection of noradrenaline, 5-hydroxytryptamine and carbachol into one lateral cerebral ventricle were investigated in conscious sheep at ambient air temperatures of 0 and 40 'C. The dose rates used were known to produce predictable changes in thermoregulation in sheep.2. The changes in body temperature, respiratory frequency and shivering caused by the intracerebroventricular (i.c.v.) injections of noradrenaline, 5-hydroxytryptamine and carbachol were as reported previously.3. The cardiovascular and renal responses of the sheep at both high and low ambient temperatures were consistent for each transmitter indicating that these activities had no major dependence on the type of thermoregulatory response.4. i.c.v. injection of noradrenaline increased heart rate and decreased pulse pressure but caused no change in mean arterial blood pressure (B.P.). Urine flow rate, sodium clearance, potassium clearance and osmolal clearance were decreased whereas solute-free water reabsorption was unaltered.5. ic.v. injection of 5-hydroxytryptamine caused no significant alterations in either cardiovascular or renal function.6. i.c.v. injection of carbachol increased systolic and diastolic B.P., heart rate and haematocrit. Sodium, potassium and osmolal clearances were increased after administration of carbachol.7. The changes in renal function after noradrenaline and carbachol injection could be explained by the concurrent changes in cardiovascular function.

Changes in Renal Haemodynamics and Electrolyte Excretion after Intraventricular Infusion of Carbachol in Conscious Sheep

“…These responses were similar to those produced by single ICV injections of carbachol into sheep held at ambient temperatures of 0 and 40°C [Beal and Bligh, 1979]. Mean R.P.F.…”

“…The infusion of carbachol into one lateral cerebral ventricle of the sheep always caused increases in arterial blood pressure, heart rate and haematocrit. These responses were similar to those produced by single ICV injections of carbachol into sheep held at ambient temperatures of 0 and 40°C [Beal and Bligh, 1979].…”

“…The increase in potassium excretion rate resulted mainly from increased potassium secretion possibly stimulated by increased distal sodium delivery and by increased vasopressin levels. The observed effects of ICV carbachol infusion resembled those previously reported for ICV infision of hyperosmotic sodium solutions.The renal excretion of electrolytes particularly that of sodium was increased for some hours after a single injection of carbachol into the third ventricle of rats [Dorn, Antunes-Rodrigues and McCann, 1970] and the lateral ventricle of sheep [Beal and Bligh, 1979]. As changes in renal haemodynamics were not monitored in either study it could not be deduced whether this increase in sodium excretion resulted from an increased rate of sodium filtration at the glomerulus and/or a reduced rate of sodium reabsorption in the nephron.…”

“…The renal excretion of electrolytes particularly that of sodium was increased for some hours after a single injection of carbachol into the third ventricle of rats [Dorn, Antunes-Rodrigues and McCann, 1970] and the lateral ventricle of sheep [Beal and Bligh, 1979]. As changes in renal haemodynamics were not monitored in either study it could not be deduced whether this increase in sodium excretion resulted from an increased rate of sodium filtration at the glomerulus and/or a reduced rate of sodium reabsorption in the nephron.…”

“…As changes in renal haemodynamics were not monitored in either study it could not be deduced whether this increase in sodium excretion resulted from an increased rate of sodium filtration at the glomerulus and/or a reduced rate of sodium reabsorption in the nephron. Injection of carbachol into the lateral ventricle also causes elevation of arterial blood pressure in rats and sheep [Hoffman and Phillips, 1977;Beal and Bligh, 1979] which in turn could lead to an increase in renal blood flow (R.B.F.) and glomerular filtration rate (G.F.R.).…”