Related Experiment Videos
Ryanodine-, IP3- and NAADP-dependent calcium stores control acetylcholine release
P Chameau1, Y Van de Vrede, P Fossier
1Laboratoire de Neurobiologie Cellulaire et Moléculaire, C.N.R.S., 91198 Gif-sur-Yvette cedex, France.
Pflugers Archiv : European Journal of Physiology
|November 20, 2001
Summary
Calcium (Ca2+) release from different intracellular stores modulates acetylcholine (ACh) release in Aplysia neurons. Distinct Ca2+ pools, activated by inositol trisphosphate (IP3) and nicotinamide adenine dinucleotide phosphate (NAADP), regulate presynaptic Ca2+ levels.
Area of Science:
- Neuroscience
- Cellular Biology
- Neurophysiology
Background:
- Intracellular calcium (Ca2+) signaling plays a crucial role in neurotransmitter release.
- Different calcium (Ca2+) release mechanisms, including those involving inositol trisphosphate (IP3) and nicotinamide adenine dinucleotide phosphate (NAADP), are known to exist.
Purpose of the Study:
- To investigate the roles of distinct intracellular Ca2+ stores in modulating acetylcholine (ACh) release at a presynaptic terminal.
- To determine if Ca2+ release via IP3 and NAADP pathways differentially impacts presynaptic Ca2+ concentration and subsequent transmitter release.
Main Methods:
- Electrophysiological recordings of inhibitory postsynaptic currents in Aplysia californica buccal ganglion.
- Intracellular injections of signaling molecules (IP3, NAADP, cyclic ADP-ribose) into presynaptic neurons.
- Pharmacological manipulation using specific antagonists for calcium-induced calcium release (CICR) and IP3 receptors.
- Measurement of intracellular Ca2+ ([Ca2+]i) changes using the fluorescent dye rhod-2.
Main Results:
- Injections of IP3 and NAADP into presynaptic neurons enhanced evoked inhibitory postsynaptic currents, indicating modulation of ACh release.
- Ryanodine and heparin selectively blocked IP3-mediated potentiation but not NAADP-mediated effects, suggesting distinct Ca2+ pools.
- Measurements confirmed that IP3, NAADP, and cyclic ADP-ribose induced transient increases in intracellular Ca2+.
- NAADP-induced Ca2+ increases were resistant to antagonists of ryanodine receptors (RyR) and IP3 receptors.
Conclusions:
- Presynaptic terminals contain distinct, functionally independent Ca2+ stores regulated by RyR, IP3 receptors, and NAADP.
- These differentially regulated Ca2+ stores contribute to the precise control of presynaptic Ca2+ concentration, thereby regulating transmitter release.
- NAADP-activated Ca2+ release represents a distinct pathway independent of canonical IP3 and RyR-mediated release mechanisms in this synapse.