Fig. 5. Model for dopamine-mediated regulation of pancreatic α- and β-cell hormone secretion.
a In α-cells, low concentrations of local dopamine (DA) are sufficient to stimulate high-affinity D2-like receptors to diminish glucagon secretion via inhibitory Gαi-mediated intracellular signaling. At higher concentrations, there is sufficient DA to trigger the activation of stimulatory β-adrenergic receptors. This results in increased glucagon secretion via stimulatory Gαs-mediated signaling. b In β-cells, at low DA concentrations, DA primarily signals through the high-affinity D2-like receptors to inhibit insulin secretion. At higher DA concentrations, the lower-affinity α2A-adrenergic receptors are also activated to maintain overall inhibition of insulin release since both high- and low-affinity catecholamine receptors are coupled to inhibitory Gαi.