RETROGRADE SIGNALING IN THE DEVELOPMENT AND MODIFICATION OF SYNAPSES

Retrograde signaling from the postsynaptic cell to the presynaptic neu ron is essential for the development, maintenance, and activity-depend ent modification of synaptic connections. This review covers various f orms of retrograde interactions at developing and mature synapses. Fir st, we discuss evidence for early retrograde inductive events during s ynaptogenesis and how maturation of presynaptic structure and function is affected by signals from the postsynaptic cell. Second, we review the evidence that retrograde interactions are involved in activity-dep endent synapse competition and elimination in developing nervous syste ms and in long-term potentiation and depression at mature synapses. Th ird, we review evidence for various forms of retrograde signaling via membrane-permeant factors, secreted factors, and membrane-bound factor s. Finally, we discuss the evidence and physiological implications of the long-range propagation of retrograde signals to the cell body and other parts of the presynaptic neuron.