The role of the sympathetic innervation in the control of plasma glucagon concentration in the calf

Abstract

SUMMARY1. The extent to which the splanchnic sympathetic innervation is implicated in the control of plasma glucagon concentration has been investigated in the young calf.2. Stimulation of the peripheral ends of both splanchnic nerves (0.5-10.0 c/s for 10 min) caused an abrupt increase in plasma glucagon concentration in adrenalectomized calves 3-5 weeks after birth. This effect was found to be statistically significant (P < 0-01) at each of these frequencies. In calves tested during the first 24 hr after birth comparatively small responses were obtained.3. The hyperglyeaemia produced by splanchnic nerve stimulation in older calves caused an abrupt rise in plasma insulin concentration when stimulation was discontinued but insulin release was completely inhibited throughout the period of stimulation at all frequencies tested.4. It is concluded that tonic changes in sympathetic efferent activity are likely to modify plasma glucagon concentration in the normal conscious calf.

Descending pathways from hypothalamus to dorsal motor vagus and ambiguus nuclei in the rat

“…In summary, electrical or chemical stimulation of the ih elicits an insulin release from the pancreas, but does not change glucagon levels [19,37,39,40], whereas stimulation of the vmh leads to an increase of glucagon secretion and minor changes in insulin levels. Likewise it was reported that vagal nerve stimulation results in insulin secretion [4,6,20] and splanchnic nerve stimulation in glucagon release and suppression of insulin secretion [7,8]. The effect of blocking agents like atropin [20] or hexamethonium [39] further supports the theory that insulin and glucagon secretion are under control of parasympathetic and sympathetic autonomous components, respectively.…”

The hypothalamus, intrinsic connections and outflow pathways to the endocrine system in relation to the control of feeding and metabolism

“…Either electrical or chemical stimulation of the ventromedial hypothalamic nucleus (VMH), on the other hand, elicits a rise in plasma glucagon levels mediated by sympathetic components of the autonomic nervous system that are blocked by the ganglion blocker hexamethonium (Berthoud and Jeanrenaud, 1979;Steffens, 1981). The same effects on glucagon levels can be achieved by applying electrical current to the splanchnic nerve (Bloom et al, 1973;Bloom and Edwards, 1975). The role of the dorsomedial hypothalamic nucleus (DMH) in glucose homeostasis is far less clear.…”

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

“…The fact that insulin release is inhibited during splanchnic nerve stimulation, but occurs immediately thereafter, to an extent that is determined by the intensity of the hyperglycaemic stimulus at that time (Bloom, Edwards & Vaughan, 1973;Bloom & Edwards, 1975, was employed to assess the extent to which the parasympathetic innervation is implicated in the insulin response to endogenous hyperglycaemia. If release of insulin in response to a rise in plasma glucose L. …”