Attraction of nerve fiber outgrowth from sympathetic ganglia to heart auricles in tissue culture

Sympathetic chain ganglia of 3-day-old rats were cultured in Rose chambers for 5 days. Each chamber contained either two ganglia or a ganglion and a piece of heart atrium. Visual examination failed to show an increased density or length of nerve fibers growing towards the other explant. However, actual measurements showed that the length of nerve fiber outgrowth towards the atrium explant was about 10% longer than the mean outgrowth to all directions, the difference being statistically significant (P< 0.0001). In ganglion-ganglion pair cultures the nerve fiber outgrowth towards the other ganglion tended to be shorter than that to other directions. It is tentatively concluded that atrium explants exert a growth-promoting influence on sympathetic nerve fibers in cultures, possibly due to diffusion of a growth-promoting substance from the atrium explant.