Cyclic ADP-ribose and calcium-induced calcium release regulate neurotransmitter release at a cholinergic synapse of Aplysia.
1. Presynaptic injection of cyclic ADP-ribose (cADPR), a modulator of the ryanodine receptor, increased the postsynaptic response evoked by a presynaptic spike at an identified cholinergic synapse in the buccal ganglion of Aplysia californica. 2. The statistical analysis of long duration postsynaptic responses evoked by square depolarizations of the voltage-clamped presynaptic neurone showed that the number of evoked acetylcholine (ACh) quanta released was increased following cADPR injection. 3. Overloading the presynaptic neurone with cADPR led to a transient increase of ACh release followed by a depression. 4. cADPR injections did not modify the presynaptic Ca2+ current triggering ACh release. 5. Ca2+ imaging with the fluorescent dye rhod-2 showed that cADPR injection rapidly increased the free intracellular Ca2+ concentration indicating that the effects of cADPR on ACh release might be related to Ca2+ release from intracellular stores. 6. Ryanodine and 8-amino-cADPR, a specific antagonist of cADPR, decreased ACh release. 7. ADP-ribosyl cyclase, which cyclizes NAD+ into cADPR, was present in the presynaptic neurone as shown by reverse transcriptase-polymerase chain reaction experiments. 8. Application of NAD+, the substrate of ADP-ribosyl cyclase, increased ACh release and this effect was prevented by both ryanodine and 8-amino-cADPR. 9. These results support the view that Ca(2+)-induced Ca2+ release might be involved in the build-up of the Ca2+ concentration which triggers ACh release, and thus that cADPR might have a role in transmitter release modulation.
Mothet
J P
JP
Laboratoire de Neurobiologie Cellulaire et Moléculaire, CNRS, Gif-sur-Yvette, France.
Fossier
P
P
Meunier
F M
FM
Stinnakre
J
J
Tauc
L
L
Baux
G
G
D000109:Acetylcholine / Q000378:metabolism; D000246:Adenosine Diphosphate Ribose / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D001048:Aplysia / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D036563:Cyclic ADP-Ribose; D004594:Electrophysiology; D005456:Fluorescent Dyes; D017952:Ganglia, Invertebrate / Q000187:drug effects / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009243:NAD / Q000378:metabolism / Q000494:pharmacology; D018377:Neurotransmitter Agents / Q000378:metabolism*; D010275:Parasympathetic Nervous System / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D016133:Polymerase Chain Reaction; D017661:Receptors, Presynaptic / Q000187:drug effects; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects; D013569:Synapses / Q000187:drug effects / Q000378:metabolism*
D005456:Fluorescent Dyes; D018377:Neurotransmitter Agents; D017661:Receptors, Presynaptic; D019837:Ryanodine Receptor Calcium Release Channel; D009243:NAD; D036563:Cyclic ADP-Ribose; D000246:Adenosine Diphosphate Ribose; D000109:Acetylcholine; D002118:Calcium