Restoration of serotonergic innervation underlies the behavioral effects of raphe grafts.

It has been previously demonstrated that an embryonic raphe grafted into a serotonin-depleted hippocampus restores normal serotonin innervation of the hippocampus and behaviors associated with serotonin. To test the possibility that the behavioral effects of these grafts result from non-specific actions of the grafted tissue or the grafting procedure itself, we compared raphe grafts with septal grafts, in serotonin-depleted rats. We also compared the effects of a serotonin synthesis inhibitor, p-chlorophenylalanine, on the behavior of normal, serotonin-depleted and raphe-grafted rats. The results indicate that the bulk of behavioral effects of raphe grafts are due to the serotonergic nature of the graft.