Synchronous calcium oscillations in cerebellar granule cells in culture mediated by NMDA receptors.

ABSTRACT

The concentration of cytosolic Ca2+ ([Ca2+]i) was monitored in cerebellar granule cell cultures by digital imaging of fura-2 loaded cells. In the presence of Mg2+, cells grown in low K+ cultures responded to N-methyl-D-aspartate (NMDA) with uniform increases in [Ca2+]i from a stable basal [Ca2+]i. In contrast, in Mg(2+)-free medium, low K+ cultures showed spontaneous, synchronized [Ca2+]i oscillations from 4 days in culture. The oscillations were rapidly blocked by Mg2+, D,L-2-amino-5-phosphonovalerate, or tetrodotoxin. The development of oscillatory behaviour depended on the culture conditions and was not observed in cultures grown in high K+. These data show a high degree of connectivity established within 4 days in culture by dissociated granule cells allowing synchronized activity mediated through synaptic mechanisms.