Pancreatic B cells are bursting, but how?

Insulin secretogogues have long been known to stimulate and modulate bursting electrical activity in pancreatic islet B cells and thereby supply extracellular Ca2+ for the exocytosis of insulin. Recent results have ruled out a long-held hypothesis for the mechanism of burst formation that postulated key roles for intracellular Ca2+ accumulation and activation of Ca(2+)-activated K+ channels. Here, we present an alternative hypotheses based on a persistent Ca2+ conductance and, possibly, phasic activation of ATP-sensitive K+ channels. These hypotheses are compared with mechanisms of bursting proposed for invertebrate and mammalian neurons.