Subcellular Topography and Plasticity of Gap Junction Distribution on Astrocytes

Abstract

The aim of this chapter is to characterize the cellular and subcellular morphology of the astrocytic network and its plasticity with respect to cellular connectivity. As will be shown, the plasticity of gap junction coupling is a dynamic process, which enables astrocytes to alter the junctional-coupling pattern with a very short latency on neural induction. This was studied by immunohistochemistry using antibodies against connexin43, the major astrocytic gap junction protein.1 Morphological characterization of astrocytes allows analysis of subcellular gap junction distribution on astrocytic surfaces. Surface-to-volume analysis of astrocytes reveals that predominantly lamellae, flat sheet-like or finger-like protrusions of astrocytic processes and cell body form gap junctions and frequently build coupled ensheathments around synapses.2 Data will be shown that gap junctions exist between different cells, but that they also couple processes and lamellae of one cell. Hence, we conclude that astrocytic gap junctions do not only form a system of intercellular junctions. Rather, gap junctions serve to build astrocytic compartments regardless of whether processes and lamellae of different cells are connected or parts of the same cell are coupled.