An orally administered serotonin-4 (5-HT4) receptor agonist, mosapride citrate (MOS), promotes enteric neurogenesis in anastomoses after gut surgery. We performed gut surgery and transplanted 2 × 10(5) neural stem cells (NSCs) from the embryonic central nervous system after marking them with the cell linker, PKH26. We found that neurons differentiated from transplanted NSCs (PKH [+]) and newborn enteric neurons differentiated from mobilized (host) NSCs (YFP [+]) in the deep granulation tissue of the anastomotic ileum. MOS significantly increased the number of PKH (+) and YFP (+) neurons by 2.5-fold (P < 0.005) (n = 4). The distribution patterns of PKH (+) neurons and YFP (+) neurons were similar along the depth of the anastomosis. A 5-HT4 receptor antagonist, SB-207266, abolished these effects of MOS (n = 4). Our results indicate that neurogenesis from transplanted NSCs is potentiated by activation of 5-HT4 receptors. Thus, a combination of drug administration and cell transplantation could be more beneficial than cell transplantation alone in treating Hirschsprung's disease and related disorders.