Electrical characteristics of pancreatic islet cells.
1. The electrical properties of mouse pancreatic islet cells have been explored in vitro using a single intracellular micro-electrode for both voltage recording and current injection. 2. The frequency of spontaneous electrical activity induced in islet cells by concentrations of D-glucose greater than 2-8 mM was enhanced by depolarizing, and reduced by hyperpolarizing, current injection.  Post-stimulus inhibition and facilitation were also observed. 3. Intracellular current injection evoked a spike potential in Krebs solution containing a low D-glucose concentration (2-8mM), and in glucose-free, but not Ca-free solution.  Evoked spikes were observed in approximately 10% of the cell population impaled. 4. The relationship between the rate of rise of an evoked spike and membrane potential displacement by intracellular current injection a sigmoid curve suggesting the presence of an inactivation process in spike potential genesis. 5. High [K]o, 30-50mM, induced electrical activity rarely, and then only transiently, thereafter blocking it; conditioning hyperpolarizing current tended to restore spike activity. 6. D-600, 5 times 10-minus 5M, blocked the electrical activity induced by D-glucose, tolbutamide or current injection; these inhibitory effects were reversed by a threefold increase in [Ca]o to 7-68 mM. 7. From these results it is concluded that the electrical activity induced in islet cells by Dglucose, tolbutamide and current injection is due mainlu to Ca-2+ influx and is dependent on the level of the membrane potential
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002118:Calcium / Q000494:pharmacology / Q000502:physiology; D004558:Electric Stimulation; D005711:Gallopamil / Q000494:pharmacology; D005947:Glucose / Q000494:pharmacology; D066298:In Vitro Techniques; D007515:Islets of Langerhans / Q000166:cytology / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008839:Microelectrodes; D011188:Potassium / Q000494:pharmacology; D014044:Tolbutamide / Q000494:pharmacology
D005711:Gallopamil; D014044:Tolbutamide; D005947:Glucose; D011188:Potassium; D002118:Calcium