ABSTRACT
Molecular and biophysical studies indicate that gap junctions comprise a family of structurally related intercellular channels that are dynamically gated by a variety of agents. Some gap junction channels are strongly gated by voltage. This chapter presents a data on the voltage-dependent properties of gap junctions in larval salivary glands of Drosophila melanogaster. It demonstrates the gap junctions in Drosophila salivary glands are strongly gated by both transjunctional potential and inside-outside potential. Steady-state and kinetic data indicate that transjunctional potential and inside-outside potential sensitivities are distinguished by their polarity dependence and kinetics. The complex topological arrangement of cells within tissues creates multiple pathways for cell-to-cell current flow, thereby precluding precise quantification of junctional conductance. Simplified coupling geometries exemplified by invertebrate giant fiber systems and isolated cell pair preparations allows the unambiguous determination of junctional, as well as the nonjunctional conductances when used in conjunction with dual current-clamp or dual voltage-clamp techniques.
