Multiple Synapses

Cross references: 
Glutamate    Excitation   GABA   Inhibition     


Until yesterday I didn't realize that a single neuron could receive, not just multiple, but a variety of synapses on its dendrites.  It turns out that it's quite possible for a neuron to receive both excitatory and inhibitory synapses. 
    My comment:
    This puts the Excitation vs. Inhibition  dichotomy into question. 

Searching Google for "multiple synapses" found 5,500,00 references:   

Occurrence and three-dimensional structure of multiple synapses ...     
    "Light microscopic analyses of Golgi preparations revealed that about 20% of the axons occurring in stratum radiatum come into close apposition with two to four different dendrites of a target CA1 cell."  
    "Serial electron microscopy revealed that 24% of the individual axonal boutons in stratum radiatum make synapses with multiple dendritic spines arising from either the same or different dendritic segments. 
    Two adjacent boutons of the same axon could also be found to synapse with different spines of the same dendrite."    

Multiple synaptic connections of a single neuron change differentially ...
    "Thus, synaptic connections of the single interneuron RPeD1 change differentially throughout the adult life ..."  

The Formation of Multi-synaptic Connections by the Interaction of ...
    "Structural plasticity, on the one hand, refers to the outgrowth and retraction of axons and dendrites, which is primarily taking place during developmental phases or after major injuries of the network structure [1]. On the other hand, it refers to the process of creating and removing synapses, which is the predominant process in adult networks [12]. "  

How does one neuron with multiple synapses decide what synapse to ... 
    " According to Dale's principle, all of the synapses emanating from a single neuron are of the same type. When the neuron fires an action potential, each synapse is activated with approximately the same probability. If one synapse is activated and not another, it is due to synaptic variability arising from things like molecular noise and short term synaptic depression."  

Frontiers | Why Neurons Have Thousands of Synapses, a Theory of ... 
    "Pyramidal neurons represent the majority of excitatory neurons in the neocortex. Each pyramidal neuron receives input from thousands of excitatory synapses that are segregated onto dendritic branches. The dendrites themselves are segregated into apical, basal, and proximal integration zones, which have different properties." 

Synaptic Formation | BioNinja 
    "Neural pruning involves the loss of unused neurons (by removing excess axons and eliminating their synaptic connections)
  • Infant and adult brains typically have the same total number of neurons (roughly 100 billion neurons in total)
  • However infant brains form vastly more synaptic connections (approximately twice the number found in adult brains)

Synapse-Specific Regulation Revealed at Single Synapses Is ...  
    "Synaptic transmission and its activity-dependent modulation, known as synaptic plasticity, are fundamental processes in nervous system function. Neurons may receive thousands of synaptic contacts, but synaptic regulation may occur only at individual or discrete subsets of synapses, which may have important consequences on the spatial extension of the modulation of synaptic information." 

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