Dihydropyridine Receptors and Type 1 Ryanodine Receptors Constitute the Molecular Machinery for Voltage-Induced Ca2+ Release in Nerve Terminals

• Published in: The Journal of neuroscience Vol. 26; no. 29; pp. 7565 - 7574
• Main Authors: De Crescenzo, Valerie, Fogarty, Kevin E, ZhuGe, Ronghua, Tuft, Richard A, Lifshitz, Lawrence M, Carmichael, Jeffrey, Bellve, Karl D, Baker, Stephen P, Zissimopoulos, S, Lai, F. Anthony, Lemos, Jose R, Walsh, John V., Jr
• Format: Journal Article
• Language: English
• Published: United States Soc Neuroscience 19-07-2006; Society for Neuroscience
• Subjects: 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
• ISSN: 0270-6474; 1529-2401
• 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+.