J Neurophysiol (January 1, 2003). 10.1152/jn.00337.2002
Submitted on Submitted 6 May 2002; accepted in final form 23 August 2002

Optical Analysis of Depolarization Waves in the Embryonic Brain: A Dual Network of Gap Junctions and Chemical Synapses

Departments of  ¹Physiology and  ²Neurobehavioral Medicine, Tokyo Medical and Dental University, Graduate School and Faculty of Medicine, Tokyo 113-8519, Japan

Momose-Sato, Yoko, Naohisa Miyakawa, Hiraku Mochida, Shinichi Sasaki, and Katsushige Sato. Optical Analysis of Depolarization Waves in the Embryonic Brain: A Dual Network of Gap Junctions and Chemical Synapses. J. Neurophysiol. 89: 600-614, 2003. Correlated neuronal activity plays a fundamental role in the development of the CNS. Using a multiple-site optical recording technique with a voltage-sensitive dye, we previously described a novel type of depolarization wave that was evoked by cranial or spinal nerve stimulation and spread widely over the whole brain region in the chick embryo. We have now investigated developmental expression and neuronal network mechanisms of this depolarization wave by applying direct stimulation to the brain stem or upper cervical cord of E5-E11 embryos, which elicited wave activity similar to that evoked by nerve stimulation. Spatial distribution patterns of the depolarization wave changed dynamically with development, and this change appeared to be related to the regional differences in neuronal differentiation. The depolarization wave was completely eliminated by application of either gap junction blockers or an N-methyl-D-aspartate (NMDA)-receptor antagonist, indicating that functions of both gap junctions and NMDA receptors are indispensable for wave propagation. A possible interpretation of the results is that dual networks of gap junctions and chemical synaptic coupling mediate large-scale depolarization waves in the developing chick CNS.