Artificial electrotonic coupling affects neuronal firing patterns depending upon cellular characteristics.

While there have been numerous theoretical studies indicating that electrotonic coupling via gap junctions interacts with the intrinsic characteristics of the coupled neurons to modify their electrical behaviour, little experimental evidence has been provided in coupled mammalian neurons. Using an artificial electrotonic junction, two distant uncoupled neurons were coupled through the computer, and the coupling conductance was varied. Tonically firing CA1 hippocampal pyramidal neurons reduced their spike firing frequency when coupled to thalamic or pyramidal cells, showing that the electrical coupling can be considered as a low-pass filter. The strength of coupling needed to entrain spike bursts of pyramidal neurons was considerably lower than the coupling needed to synchronize two neurons with different cellular characteristics (thalamic and pyramidal cells). Coupling promoted burst firing in a non-bursting cell if it was coupled to a spontaneously bursting neuron. These results support modelling studies that indicate a role for gap-junctional coupling in the synchronization of neuronal firing and the expression of low-frequency bursting.