Close communication between the subependymal serotonergic plexus and the neurogenic subventricular zone

Although many studies have appeared on the mechanisms of neurogenesis in the adult mammalian central nervous system, the challenge remains to identify the factors controlling this process. Among numerous factors, which have been described to influence neurogenesis, serotonin (5-hydroxytryptamine, 5-HT) has received considerable attention. 5-HT drug manipulations and their effects on neurogenesis have revealed that 5-HT contributes to adult neurogenesis. An interesting but relatively unexplored detail is the presence of an extensive plexus of 5-HT containing fibers in the subventricular zone, the main neurogenic brain structure besides the dentate gyrus in the hippocampal formation. A dense plexus of 5-HT fibers surrounds the subventricular zone, separating this region from the adjacent structures of the lateral ventricle. This close anatomical relationship suggests an important functional role for 5-HT in influencing cell proliferation in the subventricular zone. Here, we review the literature and propose that subependymal plexus is part of an intrinsic brain mechanism which controls the subventricular zone cell proliferative capacity by modulating 5-HT release.