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Differences in membrane structure between excitatory and inhibitory synapses in the cerebellar cortex
Author(s) -
Landis Dennis M. D.,
Reese T. S.
Publication year - 1974
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.901550107
Subject(s) - excitatory postsynaptic potential , inhibitory postsynaptic potential , excitatory synapse , biology , neuroscience , postsynaptic potential , synapse , purkinje cell , cerebellar cortex , synaptic pharmacology , axon , parallel fiber , synaptic vesicle , dendrite (mathematics) , dendritic spine , climbing fiber , cerebellum , biophysics , vesicle , synaptic augmentation , membrane , hippocampal formation , receptor , biochemistry , geometry , mathematics
Several synapses of known physiological action are antomically segregated in the cerebellar cortex and are readily identified in freeze‐fracture preparations. Excitatory synapses, such as the parallel fiber‐to‐Purkinje spine synapse, climbing fiber‐to‐Purkinje spine synapse, and mossy or climbing fiber‐to‐granule cell dendrite synapse, were characterized by small aggregates of large particles on the cytoplasmic half of the presynaptic membrane, by a distinctly widened synaptic cleft, and by a large aggregate of particles on the external half of the postsynaptic membrane. Inhibitory synapses, such as the stellate cell axon‐to‐Purkinje dendrite synapse and the basket cell axon‐to‐Purkinje soma synapse, had no comparable specialization of either the pre‐ and postsynaptic membrane. The striking contrast in membrane structure at excitatory and inhibitory synaptic contacts presumably reflects differences in either the composition or organization of membrane proteins integral to synaptic function. Puncta adhaerentia between granule cell dendrites in cerebellar glomeruli were characterized by particles aggregated on the external half of both apposed membranes and were further differentiated from synaptic contacts by the smaller size of the particles. Protuberances on the external half of the presynaptic membrane were either small and coextensive with the synaptic contact or were larger and surrounded it; it is suggested that the small protuberances are synaptic vesicle sites whereas the large ones are coated vesicle sites.