Effects of vagal stimulation, vagotomy and adrenalectomy on release of insulin in the rat.

To evaluate the physiological role of the vagus nerve in the secretion of insulin in the rat, changes in plasma levels of insulin and sugar were examined after vagotomy with and without adrenalectomy. Male rats, fasted for 22 h, weighing about 300 g and anaesthetized with pentobarbitone sodium were used. Thirty minutes after unilateral or bilateral adrenalectomy, the first blood sample was taken just before pancreatic vagotomy and a second sample was taken 15 min after vagotomy. Pancreatic vagotomy significantly decreased levels of plasma insulin in bilaterally adrenalectomized rats. It was also confirmed that electrical stimulation of the pancreatic vagus nerve provoked an increase in levels of insulin associated with a reduction of carbohydrates in the blood. These observations support the theory that there is a vagal mechanism which modulates the secretion of insulin and suggest that the vagal mechanism is a potent factor although such a mechanism may be masked by the activity of the adrenal gland.