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

1. 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 hyperglycaemia 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.