Facilitation of the presynaptic calcium current at an auditory synapse in rat brainstem

J Physiol. 1998 Nov 1;512 ( Pt 3)(Pt 3):723-9. doi: 10.1111/j.1469-7793.1998.723bd.x.


1. The presynaptic calcium current (IpCa) was recorded from the calyx of Held in rat brainstem slices using the whole-cell patch clamp technique. 2. Tetanic activation of IpCa by 1 ms depolarizing voltage steps markedly enhanced the amplitude of IpCa. Using a paired pulse protocol, the second (test) response was facilitated with inter-pulse intervals of less than 100 ms. The facilitation was greater at shorter intervals and was maximal (about 20%) at intervals of 5-10 ms. 3. When the test pulse duration was extended, the facilitation was revealed as an increased rate of IpCa activation. From the current-voltage relationship measured at 1 ms from onset, facilitation could be described by a shift in the half-activation voltage of about -4 mV. 4. IpCa facilitation was not attenuated when guanosine-5'-O-(3-thiotriphosphate) (GTPgammaS) or guanosine-5'-O-(2-thiodiphosphate) (GDPbetaS) was included in the patch pipette, suggesting that G-proteins are not involved in this phenomenon. 5. On reducing [Ca2+]o, the magnitude of facilitation diminished proportionally to the amplitude of IpCa. Replacement of [Ca2+]o by Ba2+ or Na+, or buffering of [Ca2+]i with EGTA or BAPTA attenuated IpCa facilitation. 6. We conclude that repetitive presynaptic activity can facilitate the presynaptic Ca2+ current through a Ca2+-dependent mechanism. This mechanism would be complementary to the action of residual Ca2+ on the exocytotic machinery in producing activity-dependent facilitation of synaptic responses.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Auditory Pathways / cytology
  • Auditory Pathways / drug effects
  • Auditory Pathways / physiology*
  • Brain Stem / cytology
  • Brain Stem / drug effects
  • Brain Stem / physiology*
  • Calcium Channels / drug effects
  • Calcium Channels / physiology*
  • Electric Stimulation
  • Electrophysiology
  • Enzyme Inhibitors / pharmacology
  • Guanosine 5'-O-(3-Thiotriphosphate) / pharmacology
  • Guanosine Diphosphate / analogs & derivatives
  • Guanosine Diphosphate / pharmacology
  • In Vitro Techniques
  • Kinetics
  • Membrane Potentials / drug effects
  • Membrane Potentials / physiology
  • Patch-Clamp Techniques
  • Phosphoric Monoester Hydrolases / antagonists & inhibitors
  • Phosphotransferases / antagonists & inhibitors
  • Rats
  • Rats, Wistar
  • Receptors, Presynaptic / drug effects*
  • Synapses / drug effects
  • Synapses / physiology*
  • Thionucleotides / pharmacology


  • Calcium Channels
  • Enzyme Inhibitors
  • Receptors, Presynaptic
  • Thionucleotides
  • Guanosine Diphosphate
  • Guanosine 5'-O-(3-Thiotriphosphate)
  • guanosine 5'-O-(2-thiodiphosphate)
  • Phosphotransferases
  • Phosphoric Monoester Hydrolases