The phorbol ester, 12-O-tetradecanoyl-phorbol-13-acetate, enhances the evoked quanta release of acetylcholine at the frog neuromuscular junction

1987 ◽  
Vol 408 (1) ◽  
pp. 27-31 ◽  
Author(s):  
Claudia Haimann ◽  
Jacopo Meldolesi ◽  
Bruno Ceccarelli
Keyword(s):  
Neuromuscular Junction ◽  
Phorbol Ester ◽  
Frog Neuromuscular Junction ◽  
Release Of Acetylcholine

Intraterminal Ca2+ and Spontaneous Transmitter Release at the Frog Neuromuscular Junction

2001 ◽  
Vol 85 (1) ◽  
pp. 287-294 ◽  
Author(s):  
J. K. Angleson ◽  
W. J. Betz
Keyword(s):  
Neuromuscular Junction ◽  
Phorbol Ester ◽  
Intracellular Recording ◽  
Transmitter Release ◽  
The Other ◽  
Nerve Terminals ◽  
Frog Neuromuscular Junction ◽  
Tetraacetic Acid ◽  
Ratiometric Imaging ◽  
The Relationship

We investigated the relationship between intraterminal Ca2+concentration ([Ca2+]i) and the frequency of miniature end plate potentials (MEPPs) at the frog neuromuscular junction by use of ratiometric imaging of fura-2-loaded nerve terminals and intracellular recording of MEPPs. Elevation of extracellular [KCl] over the range of 2–20 mM resulted in increases in [Ca2+]i and MEPP frequency. Loading terminals with the fast and slow Ca2+-buffers bis-( o-aminophenoxy)- N,N,N′,N′-tetraacetic acid-acetoxymethyl (BAPTA-AM) and EGTA-AM resulted in equivalent reductions in the KCl-dependent increases in MEPP frequency. The [Ca2+]i dependence of MEPP frequency determined by elevation of [Ca2+]i due to application of 0.1–10 μM ionomycin was similar to that determined when [Ca2+]i was raised by increasing extracellular KCl. Measurements in 10 mM extracellular KCl revealed that application of the phorbol ester phorbol 12 myristate 13-acetetate (PMA) caused an increase in MEPP frequency while the inactive analogue, 4α-PMA, did not. PMA application also caused an increase in [Ca2+]i. The relationship between [Ca2+]i and MEPP frequency in PMA was the same as was determined by the other methods of raising [Ca2+]i. Under all conditions tested, our data revealed a low [Ca2+]i threshold for activation of transmitter release and are consistent with a K d for [Ca2+]i on the order of 1 μM.

scholarly journals Voltage-Dependent P/Q-Type Calcium Channels at the Frog Neuromuscular Junction

2011 ◽  
pp. 815-823 ◽  
Author(s):  
L. F. NURULLIN ◽  
A. R. MUKHITOV ◽  
A. N. TSENTSEVYTSKY ◽  
N. V. PETROVA ◽  
D. V. SAMIGULLIN ◽  
...  
Keyword(s):  
Neuromuscular Junction ◽  
Calcium Channels ◽  
Motor Nerve ◽  
Calcium Transient ◽  
Functional Expression ◽  
Frog Neuromuscular Junction ◽  
Motor Nerve Ending ◽  
Voltage Gated ◽  
Voltage Gated Calcium Channels ◽  
Release Of Acetylcholine

It is well known that antagonists of N-type voltage-gated calcium channels inhibit the evoked quantal release of acetylcholine in amphibian neuromuscular synapses. This, however, does not exclude the functional expression of other types of voltage-gated calcium channels in these nerve terminals. Using immunocytochemistry, we detected the expression of the 1A subunit of P/Q-type calcium channels (that is otherwise typical of mammalian motor nerve endings) in the frog neuromuscular junction. In addition, we demonstrated that the P/Q-type channel blocker ω-agatoxin IVA (20 nM) reduced the action potential-induced calcium transient and significantly decreased both spontaneous and evoked mediator release. Our data indicates the functional expression of P/Q-type calcium channels in the frog motor nerve ending which participate in acetylcholine release.

221 Presynaptic Ca2+-imaging at the frog neuromuscular junction

1996 ◽  
Vol 25 ◽  
pp. S36 ◽  
Author(s):  
M. Osanai ◽  
S. Suzuki ◽  
N. Suzuki ◽  
K. Kuba ◽  
H. Kijima
Keyword(s):  
Neuromuscular Junction ◽  
Frog Neuromuscular Junction
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