Incidence of neuronal dye-coupling in neocortical slices depends on the plane of section.

The fluorescent dye Lucifer Yellow CH was intracellularly injected into neurons in slices of guinea-pig visual neocortex which had been prepared by sectioning either in a plane normal to the pial surface (radial slices) or in a plane parallel to the pial surface (tangential slices). In radial slices 44.3% of the injections resulted in dye-coupling and the number of cells coupled to the impaled neuron per injection followed a Poisson distribution. In contrast dye-coupling was not observed in tangential slices. Incidence of dye-coupling in slices that had been sectioned in both the radial and tangential planes was the same as in intact radial slices, indicating that slicing in the radial plane induced the formation of pathways for dye movement between neurons. The results suggest that formation and/or strengthening of direct intercellular junctions between neocortical neurons may occur as a specific neuronal response to partial dendrotomy.