Spatial heterogeneity of intracellular Ca2+ signals in axons of basket cells from rat cerebellar slices

J Physiol. 1997 Aug 1;502 ( Pt 3)(Pt 3):509-19. doi: 10.1111/j.1469-7793.1997.509bj.x.

Abstract

1. Using tight-seal whole-cell recording and digital fluorescence imaging, we studied intracellular calcium (Ca2+i) 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 Ca2+i 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 [Ca2+]i 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 Ca2+i signals was also observed in K(+)-loaded cells upon depolarizing trains, suggesting that this behaviour is an intrinsic property of Ca2+i homeostasis in basket cells. 6. We conclude that depolarization of basket cell axons evokes high local Ca2+i signals in synaptic terminals, en passant varicosities and branch points. While high [Ca2+]i in presynaptic structures presumably triggers transmitter release, Ca2+i transients at branch points may control signal transmission in the axonal arborization.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Axons / chemistry
  • Axons / physiology*
  • Calcium / physiology*
  • Calcium Channels / physiology
  • Cerebellar Cortex / cytology*
  • Dendrites / chemistry
  • Dendrites / physiology
  • Image Processing, Computer-Assisted
  • Lysine / analogs & derivatives
  • Membrane Potentials / physiology
  • Neurons / chemistry
  • Neurons / physiology
  • Neurons / ultrastructure
  • Patch-Clamp Techniques
  • Population Characteristics
  • Rats

Substances

  • Calcium Channels
  • biocytin
  • Lysine
  • Calcium