Figure 1.

Model of gap junction between two cells. Connexon hemichannels dock to form intercellular channels coupling the cells, enabling cytoplasmic exchange of ions and small molecules typically less than 1000 Da in molecular weight. Undocked hemichannels, concentrated in the perinexus surrounding the gap junction [8], are typically closed but can open in response to prompts like ischemic stress. Open hemichannels thereby underpin flow of channel-permeant molecules from the cytoplasm into the extracellular space.