Lack of evidence for serotonergic effect on the cellular development of the olfactory bulb in the postnatal rat

Serotonin has been postulated to influence several developmental parameters. The potential role of serotonin in the development of the rat olfactory bulb, a simple cortical structure, was determined following selective depletion of serotonin to the olfactory bulb of neonate rats. In the neonate, 5,7-dHT was injected into the anterior olfactory nucleus to selectively destroy serotonergic axons leading to the bulb. Following survival of 5 days to 3 months, the rats were sacrificed and analyzed by immunocytochemical markers, Nissl stain, Golgi impregnation, and image analysis. The serotonin depletions had no significant effect on the cytoarchitecture of the bulb or on neuronal or glial cell growth. In addition, the depletions did not affect neuronal migration or differentiation (overall length of dendrites, branch points, or dendritic spines) of cell populations in the bulb. These findings suggest that serotonin does not, by itself, affect the overall development of cellular elements in the bulb, although this study does not rule out the possibility that serotonin may affect other parameters of development.