Haemodynamic responses to stimulation of the cardiac autonomic nerves in the anaesthetized cat with closed chest

SUMMARY1. The changes in cardiac output and mean right atrial pressure (R.A.P.) evoked at different circulating blood volumes by stimulation of the splanchnic sympathetic nerves were investigated in adrenalectomized cats under chloralose anaesthesia, with unopened chests and spontaneous respiration and with active vascular reflexes. The cardiac autonomic nerves were cut or blocked pharmacologically.2. Stimulation of the distal ends of the splanchnic nerves at 4 Hz caused aortic pressure and R.A.P. to rise to maximum values at 2 min before declining slowly. Cardiac output rose more slowly to a steady state at 3 min; at higher circulating volumes it fell initially. Although the output increments were slower in development they were better sustained than those in total peripheral resistance. The proportionate output increments were largest and the R.A.P. increments least at low circulating volumes whereas at high volumes the R.A.P. increments were large but the output changes were small or negative; the pattern of changes resembled that resulting from infusion of blood.3. Stimulation of the cardiac sympathetic nerves evoked a rise in output and a fall in R.A.P. related in magnitude to the initial value of R.A.P. On simultaneous stimulation of the splanchnic and cardiac sympathetic nerves the changes in output combined whereas the R.A.P. changes cancelled, to give output increments of 25-50 % with little change in R.A.P. at all circulating volumes.4. At high circulating volumes infusion of blood did not usually alter output or aortic pressure, but splanchnic nerve stimulation increased peripheral resistance and aortic pressure and commonly evoked a rise in left ventricular stroke work which could not be accounted for by known adrenergic mechanisms or by elevation of left ventricular end-diastolic pressure.5. Portal venous pressure was consistently elevated by splanchnic nerve stimulation; it rose more slowly than did aortic pressure or R.A.P. and was independent of a changing central venous pressure provided this did not exceed +5 mmHg. The cardiac output increments were not related to changes in the ratio between the input

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Haemodynamic responses to stimulation of the splanchnic and cardiac sympathetic nerves in the anaesthetized cat.

Barnes¹,

Bower²,

Rink³

1986

“…The right kidney was generally removed to facilitate identification of the intestinal lymph duct, which was cannulated just anterior to the renal vein, as it coursed over the ventro-medial aspect of the posterior vena cava towards the cysterna chylae. Both splanchnic nerves were cut immediately below the diaphragm and the peripheral ends enclosed in fluid electrodes constructed of silver wire and silicone rubber, as described by Barnes, Bower & Rink (1980). A standard 10-15 V square-wave stimulus (pulse width 0-5 msec) was applied throughout, usually for a period of 10 min.…”

Section: Methodsmentioning

confidence: 99%

Pancreatic endocrine responses to stimulation of the peripheral ends of the splanchnic nerves in the conscious adrenalectomized calf.

Bloom¹,

Edwards²

1980

SUMMARY1. Certain effects of stimulation of the peripheral ends of both splanchnic nerves have been investigated in unanaesthetized calves, given appropriate adrenal steroid replacement therapy.2. Splanchnic nerve stimulation at frequencies within the physiological range produced prompt rises in the concentration of glucose, pancreatic glucagon and pancreatic polypeptide in the arterial plasma. These responses were followed by a rapid rise in plasma insulin concentration when the stimulus was terminated. The extent of this rise was related to the plasma glucose concentration at that precise point in time.3. Stimulation at all frequencies tested had no effect on the concentration of vasoactive intestinal peptide in lymph collected from the intestinal duct.4. The results are discussed in relation to those obtained in previous studies in anaesthetized calves of the same age. INTTRODUCTIONRelease of catecholamines from the adrenal medulla, in response to splanchnic nerve stimulation in the calf, is now known to be substantially modified by anaesthetic agents. Barbiturate anaesthesia inhibits the output of both adrenaline and noradrenaline in response to splanchnic nerve stimulation at high frequency, although the reduction in adrenaline release is greater than that of noradrenaline. The output of adrenaline is also reduced by chloralose during splanchnic nerve stimulation at high or low frequencies, whereas that of noradrenaline is inhibited at low but potentiated at high frequencies (Edwards, Furness & Helle, 1980). Splanchnic nerve stimulation also inhibits the release of insulin and promotes that of glucagon from the pancreatic islets in anaesthetized calves (Bloom, Edwards & Vaughan, 1973;Bloom & Edwards, 1978). The present experiments were designed to examine the pancreatic neuroendocrine responses to sympathetic stimulation in conscious calves in order to assess the extent to which these might also be modified by anaesthetic agents. The results show that stimulation of the splanchnic sympathetic innerva-0022-3751/80/2280-0727 $07.50

“…Except as otherwise stated, both splanchnic nerves were cut immediately below the diaphragm. In some animals, the peripheral ends of the splanchnic nerves were enclosed in fluid electrodes constructed of silver wire and silicone rubber (Barnes, Bower & Rink, 1979) and both adrenal glands were also removed. Following adrenalectomy steroid replacement therapy was instituted by the administration of desoxycortisone acetate (0-2 mg/kg) and cortisol (10 0 mg/kg) by intramuscular injection.…”

Section: Introductionmentioning

confidence: 99%

The role of the parasympathetic system in the control of insulin release in the conscious calf.

Bloom¹,

Edwards²

1981

SUMMARY1. The effect of atropine (0-2 mg/kg) on the release of insulin from the pancreas, in response to both exogenous and endogenous hyperglycaemia, has been investigated in conscious 2-to 5-week-old calves.2. The rise in mean plasma insulin concentration in response to infusions ofglucose, which raised the concentration of glucose in the plasma by about 4 0 mmol/l, was significantly depressed in calves with cut splanchnic nerves by prior administration of atropine.3. The rise in plasma insulin concentration, which normally follows stimulation of the splanchnic nerves in the conscious calf , was almost completely suppressed by prior administration of atropine.4. These findings are discussed in relation to those of other workers with other species. The results indicate that the parasympathetic innervation to the pancreas plays an important part in the control ofinsulin release in response to hyperglycaemia.