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Spatial heterogeneity of intracellular Ca 2+ signals in axons of basket cells from rat cerebellar slices
Author(s) -
Llano Isabel,
Tan Yusuf P.,
Caputo Carlo
Publication year - 1997
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1997.509bj.x
Subject(s) - depolarization , axon , biophysics , neuroscience , axon hillock , biocytin , chemistry , neurotransmission , cerebellum , purkinje cell , electrophysiology , biology , receptor , biochemistry
1 Using tight‐seal whole‐cell recording and digital fluorescence imaging, we studied intracellular calcium (Ca i 2+ ) dynamics in cerebellar basket cells, whose dendrites, axon and presynaptic terminals are coplanar, an optimal configuration for simultaneous optical measurements of all functional domains. 2 In Cs + ‐loaded neurones, depolarizing pulses induced large Ca i 2+ transients in single axonal varicosities and synaptic terminals, contrasting with much weaker signals between varicosities or in the somato‐dendritic domain. 3 Axonal branch points consistently displayed [Ca i 2+ ] rises of similar magnitude and time course to those in axonal terminals and varicosities. 4 In biocytin‐filled basket cells, varicosity‐like swellings were present along the axon including its branch points. Thus, axonal enlargements are not due to fluorescence‐induced cell damage. 5 The spatial heterogeneity of Ca i 2+ signals was also observed in K + ‐loaded cells upon depolarizing trains, suggesting that this behaviour is an intrinsic property of Ca i 2+ homeostasis in basket cells. 6 We conclude that depolarization of basket cell axons evokes high local Ca i 2+ signals in synaptic terminals, en passant varicosities and branch points. While high [Ca 2+ ] 1 in presynaptic structures presumably triggers transmitter release, Ca i 2+ transients at branch points may control signal transmission in the axonal arborization.