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Dendro‐somatic distribution of calcium‐mediated electrogenesis in Purkinje cells from rat cerebellar slice cultures
Author(s) -
Pouille F.,
Cavelier P.,
Desplantez T.,
Beekenkamp H.,
Craig P. J.,
Beattie R. E.,
Volsen S. G.,
Bossu J. L.
Publication year - 2000
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.1469-7793.2000.00265.x
Subject(s) - depolarization , bursting , soma , biophysics , tetraethylammonium , membrane potential , chemistry , voltage dependent calcium channel , neuroscience , somatic cell , electrophysiology , calcium , purkinje cell , cerebellum , biology , potassium , biochemistry , organic chemistry , gene
1 The role of Ca 2+ entry in determining the electrical properties of cerebellar Purkinje cell (PC) dendrites and somata was investigated in cerebellar slice cultures. Immunohistofluorescence demonstrated the presence of at least three distinct types of Ca 2+ channel proteins in PCs: the α 1A subunit (P/Q type Ca 2+ channel), the α 1G subunit (T type) and the α 1E subunit (R type). 2 In PC dendrites, the response started in 66 % of cases with a slow depolarization (50 ± 15 ms) triggering one or two fast (∼1 ms) action potentials (APs). The slow depolarization was identified as a low‐threshold non‐P/Q Ca 2+ AP initiated, most probably, in the dendrites. In 16 % of cases, this response propagated to the soma to elicit an initial burst of fast APs. 3 Somatic recordings revealed three modes of discharge. In mode 1, PCs display a single or a short burst of fast APs. In contrast, PCs fire repetitively in mode 2 and 3, with a sustained discharge of APs in mode 2, and bursts of APs in mode 3. Removal of external Ca 2+ or bath applications of a membrane‐permeable Ca 2+ chelator abolished repetitive firing. 4 Tetraethylammonium (TEA) prolonged dendritic and somatic fast APs by a depolarizing plateau sensitive to Cd 2+ and to ω‐conotoxin MVII C or ω‐agatoxin TK. Therefore, the role of Ca 2+ channels in determining somatic PC firing has been investigated. Cd 2+ or P/Q type Ca 2+ channel‐specific toxins reduced the duration of the discharge and occasionallyinduced the appearance of oscillations in the membrane potential associated with bursts of APs. 5 In summary, we demonstrate that Ca 2+ entry through low‐voltage gated Ca 2+ channels, not yet identified, underlies a dendritic AP rarelyeliciting a somatic burst of APs whereas Ca 2+ entry through P/Q type Ca 2+ channels allowed a repetitive firing mainly by inducing a Ca 2+ ‐dependent hyperpolarization.