Dihydropyridine receptors and type 1 ryanodine receptors constitute the molecular machinery for voltage-induced Ca2+ release in nerve terminals

J Neurosci. 2006 Jul 19;26(29):7565-74. doi: 10.1523/JNEUROSCI.1512-06.2006.


Ca2+ stores were studied in a preparation of freshly dissociated terminals from hypothalamic magnocellular neurons. Depolarization from a holding level of -80 mV in the absence of extracellular Ca2+ elicited Ca2+ release from intraterminal stores, a ryanodine-sensitive process designated as voltage-induced Ca2+ release (VICaR). The release took one of two forms: an increase in the frequency but not the quantal size of Ca2+ syntillas, which are brief, focal Ca2+ transients, or an increase in global [Ca2+]. The present study provides evidence that the sensors of membrane potential for VICaR are dihydropyridine receptors (DHPRs). First, over the range of -80 to -60 mV, in which there was no detectable voltage-gated inward Ca2+ current, syntilla frequency was increased e-fold per 8.4 mV of depolarization, a value consistent with the voltage sensitivity of DHPR-mediated VICaR in skeletal muscle. Second, VICaR was blocked by the dihydropyridine antagonist nifedipine, which immobilizes the gating charge of DHPRs but not by Cd2+ or FPL 64176 (methyl 2,5 dimethyl-4[2-(phenylmethyl)benzoyl]-1H-pyrrole-3-carboxylate), a non-dihydropyridine agonist specific for L-type Ca2+ channels, having no effect on gating charge movement. At 0 mV, the IC50 for nifedipine blockade of VICaR in the form of syntillas was 214 nM in the absence of extracellular Ca2+. Third, type 1 ryanodine receptors, the type to which DHPRs are coupled in skeletal muscle, were detected immunohistochemically at the plasma membrane of the terminals. VICaR may constitute a new link between neuronal activity, as signaled by depolarization, and a rise in intraterminal Ca2+.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Calcium / metabolism*
  • Calcium Channel Agonists / pharmacology
  • Calcium Channel Blockers / pharmacology
  • Calcium Channels, L-Type / drug effects
  • Calcium Channels, L-Type / physiology*
  • Cell Membrane / metabolism
  • Electric Stimulation
  • Electrophysiology
  • Hypothalamus / cytology
  • Hypothalamus / metabolism
  • Immunohistochemistry
  • In Vitro Techniques
  • Mice
  • Nerve Endings / metabolism*
  • Neurons / metabolism
  • Nifedipine / pharmacology
  • Pyrroles / pharmacology
  • Ryanodine Receptor Calcium Release Channel / physiology*


  • Calcium Channel Agonists
  • Calcium Channel Blockers
  • Calcium Channels, L-Type
  • Pyrroles
  • Ryanodine Receptor Calcium Release Channel
  • FPL 64176
  • Nifedipine
  • Calcium