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

Abstract

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

Pancreatic endocrine responses to the peptides VIP and PACAP in the conscious calf

“…In the present study the response was completely suppressed when the plasma glucose concentration was raised by about 2 mmol 1-l, showing that it could not have been due to a sympathetic discharge. Such a discharge would raise plasma glucose concentration by promoting hepatic glycogenolysis (Edwards & Silver, 1970;Edwards, 1971Edwards, , 1972, inhibit secretion of insulin via an x-adrenergic mechanism (Bloom & Edwards, 1975, 1984 and produce an abrupt rise in plasma PP concentration (Bloom & Edwards, 1980, 1984. The combined administration of PACAP and acetylcholine in the present study had no significant effect on plasma glucose concentration per se.…”

Effects of the autonomic system on insulin release in response to exogenous glucose in weaned lambs.

“…The fact that a greater insulin response was obtained in lambs pre-treated with phentolamine and atropine than in atropinized lambs with cut splanchnic nerves provides further evidence of the involvement of f8-adrenoceptors in the release of insulin during hyperglycaemia in these animals. Direct electrical stimulation of the splanchnic sympathetic innervation strongly inhibits insulin release in a wide variety of species (Bloom, Edwards & Vaughan, 1973;Porte, Girardier, Seydoux, Kanazawa & Posternak, 1973;Bloom & Edwards, 1975, 1980, although it potentiates insulin release in the presence of phentolamine . As the inhibitory ac-adrenergic effect is overcome by fl-adrenergic stimulation in the conscious lamb during hyperglycaemia it seems likely that the pattern of activity in these sympathetic fibres under physiological conditions is more subtle than that which is generally imposed experimentally by continuous electrical stimulation at a pre-determined constant frequency.…”

Release of neuropeptide Y in response to splanchnic nerve stimulation in the conscious calf.

“…(b) Adrenalectomized calve8. Preparatory surgery was performed as described previously in detail (Bloom & Edwards, 1980), and involved bilateral adrenalectomy and insertion of catheters into the abdominal aorta and the inferior vena cava via the saphenous vessels. Both splanchnic nerves were cut and the peripheral ends attached to fluid electrodes.…”