PURPOSEFUL PATTERNS OF SPONTANEOUS CALCIUM TRANSIENTS IN EMBRYONIC SPINAL NEURONS

Embryonic cultured Xenopus spinal neurons generate two types of sponta neous elevation of intracellular calcium that encode developmental inf ormation in the frequency with which they are produced. Calcium spikes regulate the appearance of GABA and maturation of potassium current. Calcium waves in growth cones regulate neurite extension. Spikes and w aves are also observed in neurons differentiating in situ. Because dif ferentiation is dependent on the frequency of calcium transients, neur ons that are coactive and fire spikes in concert would be expected to differentiate together Consistent with this prediction, segmentally ar rayed clusters of putative motoneurons on the ventral aspect of the ne ural tube fire together during development.