Parasympathetic stimulation of nerves innervating the islets of the pancreas will:

The pancreatic islets receive innervation from both the sympathetic and parasympathetic nervous system. Stimulation of the parasympathetic system increases secretion of insulin from the B cells. Stimulation of the sympathetic system increases glucagon secretion from the A cells. Insulin is inhibited by sympathetic stimulation. Ref: Molina P.E. (2013). Chapter 7. Endocrine Pancreas. In P.E. Molina (Ed),Endocrine Physiology, 4e.