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

1. The role of the autonomic innervation to the pancreas in mediating the release of insulin in response to exogenous glucose has been investigated in conscious weaned lambs 4-5 months after birth. 2. The incremental rise in mean plasma insulin concentration was consistently lower in lambs with cut splanchnic nerves, which had been pre-treated with atropine (0.2 mg kg-1), than in normal control lambs, although the differences did not achieve statistical significance. 3. Pre-treatment with propranolol (0.25 mg kg-1) effectively suppressed release of insulin in response to exogenous glucose in atropinized lambs with intact splanchnic nerves, but not in atropinized lambs with cut splanchnic nerves. 4. The rise in mean plasma insulin concentration was significantly greater in lambs pre-treated with atropine (0.2 mg kg-1) and phentolamine (0.1 mg kg-1 initially, followed by 0.02 mg kg-1 min-1) than in atropinized lambs with cut splanchnic nerves. 5. It is concluded that release of insulin in response to exogenous glucose is normally modified by both sympathetic alpha-adrenergic inhibition and beta-adrenergic excitation in this species.