Sympathetic innervation of islets reciprocally regulates hormone release in response to hypoglycemia by inhibition of insulin release through activation of α2-adrenergic receptors (ADRA2A) on β-cells and stimulation of glucagon secretion by activation of β2-adrenergic receptors (ADRB2) on α-cells65. The gene discussed is GCG; the disease is Hypoglycemia.