Axonal calcium entry during fast 'sodium' action potentials in rat cerebellar Purkinje neurones.
1. Using laser-scanning confocal microscopy, fast Ca2+ transients were recorded in individual not yet myelinated axons of Purkinje neurones in cerebellar slices from young rats. Axonal Ca2+ transients could be detected during a single action potential and had progressively larger amplitudes when the number of action potentials was increased. 2. Under voltage-clamp conditions, axonal Ca2+ transients were as large as those observed in dendrites and in the cell body. Axonal Ca2+ transients were completely blocked by 100 nM of the neurotoxin omega-agatoxin IVA, indicating that they were caused by Ca2+ entry through P-type voltage-gated Ca2+ channels. 3. In conclusion, our results demonstrate action potential-mediated Ca2+ entry through voltage-gated Ca2+ channels in axons of cerebellar Purkinje neurones. Experimental evidence indicates that the resulting transient Ca2+ accumulations regulate the frequency of action potentials travelling along the axon.
I. Physiologisches Institute, Universität des Saarlandes, Homburg, Germany.
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G
Callewaert
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J
Eilers
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A
Konnerth
D000200:Action Potentials; D000818:Animals; D001369:Axons / Q000187:drug effects / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism; D003712:Dendrites / Q000378:metabolism; D066298:In Vitro Techniques; D015640:Ion Channel Gating; D017136:Ion Transport / Q000187:drug effects; D018613:Microscopy, Confocal; D011689:Purkinje Cells / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction; D012964:Sodium / Q000378:metabolism*; D013111:Spider Venoms / Q000494:pharmacology; D020867:omega-Agatoxin IVA
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D013111:Spider Venoms; D020867:omega-Agatoxin IVA; D012964:Sodium; D002118:Calcium