Abstract
Correlated neuronal activity plays a fundamental role in the development of the nervous systems. Using a multiple-site optical recording technique with a fast voltage-sensitive dye (NK2761), we found large-scale correlated activity in the embryonic rat brain. Stimulation applied to the region caudal to the obex elicited widely-spreading depolarization waves in the whole brain-spinal cord preparations dissected from E15-E17 rat embryos. The depolarization wave traveled rostrally to the forebrain and caudally to the lumbosacral spinal cord, suggesting that functional cell-to-cell communication systems mediated by the depolarization wave are widely generated in the embryonic rat central nervous system. Stimulation applied to the cranial nerves, such as the trigeminal and vagus nerves, evoked depolarization waves with similar spatio-temporal distribution patterns, indicating that the wave activity is triggered by multiple sources of external inputs. Furthermore, wave activity spontaneously occurred. Ca2+-imaging with a Ca2+ indicator (Ca green 1-AM) showed that the depolarization wave was accompanied by a Ca2+-wave. The result suggests that the wave activity provides not only electrical synchrony, but also biochemical signals associated with [Ca2+]i elevation, which might regulate developmental processes of the mammalian central nervous system. [Jpn J Physiol 55 Suppl:S140 (2005)]
