網膜アマクリン細胞間電気シナプスの機能構造の特性
詳細
Retinal amacrine cells (ACs) regulate activities of retinal ganglion cells, the output neurons to higher visual centers, through cellular mechanism of lateral inhibition in the inner plexiform layer (IPL). Electrical properties of gap junction networks between ACs in the IPL were investigated using combined techniques of intracellular recordings, Lucifer yellow and Neurobiotin injection, dual patch-clamp recordings and high voltage electron microscopy in isolated retinas of cyprinid fish. Six types of gap-junctionally connected ACs were classified after recordings of their light-evoked responses to light flashes. Among them gap junction networks of three types of ACs were studied with structure-function correlation analysis. Cellular morphology of intercellular connections between three homologous cell classes was characterized. High voltage electron microscopy (Hitachi 1250M, NIPS, Okazaki, co-operative program 2005-HVEM02) revealed localization of gap junctions between the dendritic tips of Neurobiotin-coupled cells. Receptive field size, space length constant, response latency and conduction velocity were measured. Simultaneous dual patch-clamp recordings revealed that the lateral gap junction connections between homologous ACs expressed bidirectional electrical synapses passing Na+ spikes. Lateral inhibition regulated by ACs in the IPL appears to be associated with directional extension of the dendrites and orientation of dendrodendritic gap junctions (J. Integr. Neurosci. 4(3): pp 313-340, 2005). [J Physiol Sci. 2006;56 Suppl:S91]
