Abstract
Using a multiple-site optical recording technique with a voltage-sensitive dye (NK2761), we found a widely-spreading depolarization wave in the embryonic rat central nervous system. In this study, we analyzed pharmacological characteristics of the depolarization wave. The depolarization wave was eliminated by Cd2+, Ca2+-free solution and tetrodotoxin. In experiments using antagonists of chemical neurotransmitters, it was shown that the depolarization wave was partly inhibited by glutamate-, acetylcholine-, GABA- and glycine-receptor antagonists. With combined application of these blockers, the wave was eliminated. These results suggest that chemical synaptic networks mediated by multiple neurotransmitters are responsible for wave propagation. In addition to chemical synaptic antagonists, the depolarization wave was inhibited by gap junction blockers such as octanol and 18β-glycyrrhetinic acid. In immunohistochemical studies, we observed abundant expression of connexin26 and connexin32 in E16 rat brainstems. These results suggest the possibility that a dual network of gap junctions and chemical synapses mediates the propagation of the depolarization wave in the embryonic rat brain. [Jpn J Physiol 55 Suppl:S140 (2005)]
