Beta-cell electrical activity in response to high glucose concentration.

Glucose-induced beta-cell electrical activity, recorded with glass microelectrodes, is characterized by trains of fast action potentials ("spikes"). The membrane depolarizes before each train of spikes and then repolarizes. This pattern is termed a "burst." There is a characteristic biphasic response to a square wave of 11.1 mM glucose. Pulses at higher glucose concentrations (22.2 mM or more) evoke transient, constant spike activity. The duration of this activity is lengthened and the lag period shortened in proportion to the concentration and length of the glucose pulse. The lag period between removal of glucose and the cessation of spike activity is also proportional to the glucose concentration.