Dye coupling among supraoptic nucleus neurons without dendritic damage: differential incidence in nursing mother and virgin rats.

To assess the possibility that dye coupling among neurons in hypothalamic slices might require dendrotomy, as has been suggested for neocortical neurons, dye coupling was studied in horizontally cut slices containing the supraoptic nucleus (SON). Since the dendrites of SON neurons project toward the pial surface, dendritic damage due to slicing can be avoided in the horizontal plane. Intracellular injections of Lucifer Yellow into individual SON neurons in slices from male, virgin female and lactating, mother rats yielded the following results. When dendrotomy occurred there was a significantly lower incidence of dye coupling than was observed when dendrites were intact. Higher order coupling (3 or more cells dye coupled after a single injection) was only seen among neurons without dendrotomy. Independently of dendritic damage, incidence of dye coupling in nursing mothers was reliably greater than for virgins, confirming previous results from coronal slices. The results of this study indicate that dendrotomy is not an inducer of dye coupling in SON neurons. Taken together with other recent findings, these data suggest that a reinterpretation of the effects of dendrotomy on cortical cell dye coupling may be in order.