RAPID
COMMUNICATION
Cyclic AMP Synchronizes Evoked Quantal Release at Frog Neuromuscular
Junctions
E. Bukcharaeva1,2, D. Samigullin2, E.E. Nikolsky1,2,
F. Vyskočil 3
1Kazan Medical University, Kazan, Russia, 2Kazan Institute
of Biochemistry and Biophysics, Russian Academy of Sciences, 3Institute
of Physiology, Academy of Sciences of the Czech Republic, and Department of
Animal Physiology and Developmental Biology, Charles University, Prague, Czech
Republic
Received May 4, 2000
Accepted June 15, 2000
Summary
At frog neuromuscular junction, noradrenaline (NA) shortens
the release period for evoked
quantal release acting on a b 1 receptor. To test the
hypothesis that this action of NA is mediated by cAMP, we measured the latencies
of focally recorded uni-quantal endplate currents (EPCs) after application of
dibutyryl-cAMP (db-cAMP) and adenylyl cyclase activator, forskolin. The interval
between the time when responses with minimal delay appeared and the point at
which 90 % of all latencies had occurred (P90 parameter) was
shortened in the presence of both 1x10-6 mol/l db-cAMP and
1x10-6 mol/l forskolin by about 30 %. The cAMP-induced
shortening is equal to that found after application of NA and effects of both
drugs are not additive.
Key words
Acetylcholine · Frog muscle ·
cAMP · Quantal release
Reprint requests
F. Vyskočil, Institute of Physiology, Academy of Sciences of
the Czech Republic, Vídeňská 1083, 142 20 Prague 4, Czech Republic. E-mail:
vyskocil@biomed.cas.cz
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