Trends in Neurosciences
Diversity of structure and function at mammalian central synapses
Section snippets
Structure of mammalian CNS synapses
Mammalian central synapses exist in a variety of shapes and sizes, and several examples are illustrated in Fig. 1. Some small boutons contact dendritic spines, such as those arising on pyramidal neurons in the hippocampus[22], whereas others end on the soma or smooth dendritic shafts, such as the contacts between muscle spindle afferents and motoneurons or dorsal spinocerebellar tract (DSCT) cells in the spinal cord6, 23, 24. At the other extreme, some of the largest presynaptic terminals in
The time course and probability of quantal transmitter release
The functional consequences of variations in the size and shape of synaptic specializations are potentially reflected in several parameters of synaptic transmission, in particular the probability of presynaptic transmitter-release and the amplitude and time course of the postsynaptic current. Following the arrival of an action potential at the presynaptic terminal, the secretion of a quantum of neurotransmitter from a release site occurs in an intermittent or probabilistic manner, and with a
The postsynaptic current
Spontaneous synaptic currents, thought to be generated by vesicular release of transmitter at many release sites over the surface of a neuron, and often exhibit a wide range of amplitudes and time courses within the same cell (Fig. 5). This variability at individual synaptic specializations could be caused by: the concentration and time course of neurotransmitter in the synaptic cleft; and the location and properties of the postsynaptic receptor/channels. Both of these changes could be
Concluding remarks
Experimental studies have demonstrated a large diversity of synaptic structure and function in the mammalian CNS. Although central synapses can share some basic mechanisms, the structural and functional diversity reviewed here raises the possibility that different synapses might be dominated by distinct properties linked to their particular physiological role. Further direct evidence concerning the correlation between structural and functional properties of central synapses will be extremely
Acknowledgements
We are very grateful to Alicia Fritchle for drawing Fig. 1, and to Drs Mark Bellingham, Steve Redman, Christian Stricker and Dirk van Helden for helpful comments on the manuscript. BW is supported by the National Health and Medical Research Council (Australia). FJA and REWF are supported by the National Institutes of Health (NINDS).
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Role of astrocytes in synapse formation and maturation
2021, Current Topics in Developmental BiologyCitation Excerpt :Cell adhesion molecules that transverse the synapse then anchor the pre and postsynaptic compartments together, allowing their stabilization and growth. The presynaptic terminal accumulates neurotransmitter-filled vesicles and vesicle-release machinery, while the postsynaptic terminal contains various proteinaceous scaffolds that tether neurotransmitter receptors (Schikorski & Stevens, 1997; Walmsley, Alvarez, & Fyffe, 1998). In the case of excitatory synapses, the postsynaptic terminal is often localized to a dendritic spine, which morphologically matures from a thin, filopodia-like structure to a mushroom-like shape.
Synaptic Development
2017, Conn's Translational Neuroscience