DEVELOPMENT OF ELECTRICAL EXCITABILITY IN EMBRYONIC NEURONS - MECHANISMS AND ROLES

Xenopus spinal neurons serve as a nearly ideal population of excitable cells for study of developmental regulation of electrical excitabilit y. On the one hand, the firing properties of these neurons can be dire ctly examined at early stages of differentiation and membrane excitabi lity changes as neurons mature. Underlying changes in voltage-dependen t ion channels have been characterized and the mechanisms that bring a bout these changes are being defined. On the other hand, these neurons have been shown to be spontaneously active at stages when action pote ntials provide significant calcium entry. Calcium entry provokes furth er elevation of intracellular calcium via release from intracellular s tores. The resultant transient elevations of intracellular calcium enc ode differentiation in their frequency, Recent studies have shown that different neuronal subpopulations enlist distinct mechanisms for regu lation of excitability and recruit specific programs of differentiatio n by particular patterns of activity. (C) 1998 John Wiley & Sons, Inc.