GCG and Hypoglycemia: Regarding autonomic regulation of glucagon secretion, there are three mechanisms of direct stimulation of adrenergic and cholinergic receptors from α cells, which are activated in the brain during hypoglycemia and tend to facilitate glucagon release to normalize glycemia: (1) sympathoadrenal system, which culminates with the release of Adr by the adrenal medulla; (2) islet parasympathetic nerves, eliciting a modest glucagon response; (3) islet sympathetic nerves, that provoke a robust glucagon response (126, 127).