Synaptogenesis in the adult CNS-olfactory system

The olfactory system of mammals, and the olfactory bulb (OB) in particular, provides a rich repository of new synapses. In the OB, new synapses are being formed continuously and are eliminated in high numbers relative to other regions of the mammalian central nervous system. The relatively high rate of synaptic turnover comes from several neuronal sources. Both the axonal inputs and the local interneurons are being formed continuously to replace older cells and synapses. These sources add to the normal maintenance and plastic demands of any neuronal circuit. In this chapter, some of the current knowledge regarding synaptogenesis in the olfactory system is reviewed. The topics treated include the basic architecture of the underlying neural circuits, the main synaptic types that turn over, some of the mechanisms that may be responsible for replacing large numbers of synapses, and their functional implication.