Long-term potentiation of transmitter exocytosis expressed by Ca2+-induced Ca2+ release from thapsigargin-sensitive Ca2+ stores in preganglionic nerve terminals.
We have studied whether Ca(2+)-induced Ca(2+) release (CICR) is involved in the mechanism of long-term potentiation (LTP) at nicotinic synapses of bullfrog sympathetic ganglia. Fast excitatory postsynaptic potentials (fast EPSPs) were recorded in a low-Ca(2+), high-Mg(2+) solution and quantal analysis was applied. The conditioning stimulation of the B-type preganglionic nerve at 20 Hz for 4 min consistently enhanced the amplitude and quantal content of fast EPSP for > 2 h, but only sometimes enhanced the quantal size. The LTP of quantal content produced by the conditioning tetanus was blocked by thapsigargin, a blocker of Ca(2+) pumps at Ca(2+) stores, applied before or after the conditioning tetanus, and by Xestospongin C, a blocker of inositoltrisphosphate (IP(3)) receptors, applied before the tetanus. It was not, however, blocked by ryanodine, a blocker and/or activator of ryanodine receptors, or by propranolol, a blocker of beta-adrenergic receptors. Thus the long-lasting activity of the preganglionic nerve at a high frequency causes the LTP of impulse-evoked transmitter release by the activation of CICR from thapsigargin-sensitive Ca(2+) stores in the nerve terminals. It is likely that a large Ca(2+) entry into the nerve terminals during tetanic activity primes ryanodine-insensitive Ca(2+) release channels for activation.
Cong
Ya-Lin
YL
Department of Physiology, Nagoya University, School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan.
Takeuchi
Shinpei
S
Tokuno
Hiroyuki
H
Kuba
Kenji
K
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004307:Dose-Response Relationship, Radiation; D004558:Electric Stimulation / Q000379:methods; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D005728:Ganglia, Sympathetic / Q000166:cytology*; D066298:In Vitro Techniques; D017774:Long-Term Potentiation / Q000187:drug effects* / Q000528:radiation effects; D047028:Macrocyclic Compounds; D010080:Oxazoles / Q000494:pharmacology; D017729:Presynaptic Terminals / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects; D011433:Propranolol / Q000494:pharmacology; D011892:Rana catesbeiana; D012433:Ryanodine / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology*; D013997:Time Factors
D000319:Adrenergic beta-Antagonists; D004791:Enzyme Inhibitors; D047028:Macrocyclic Compounds; D010080:Oxazoles; C108644:xestospongin A; D012433:Ryanodine; D019284:Thapsigargin; D011433:Propranolol; D002118:Calcium