RT Journal Article
SR Electronic
T1 Facilitation of transmission at the frog neuromuscular junction at O degrees C is not maximal at time zero
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 5722
OP 5724
DO 10.1523/JNEUROSCI.14-09-05722.1994
VO 14
IS 9
A1 W Van der Kloot
YR 1994
UL http://www.jneurosci.org/content/14/9/5722.abstract
AB Facilitation of quantal release has been thought to be maximal immediately after the first action potential in the presynaptic terminal. However, at the frog neuromuscular junction at 0 degrees C no facilitation was observed in response to direct nerve depolarization when the interval between stimulus pairs was less than 10 msec (Dudel, 1986), while at intervals of 20 msec and beyond, facilitation was increased (Molgo and Van der Kloot, 1991). In the present experiments, facilitation to pairs of nerve action potentials was measured both by the method of failures and by comparing the total inward postsynaptic current generated by the first and second action potentials. Facilitation was observed at intervals as short as 7 msec, but 20–30 msec was required for facilitation to reach a maximum. This suggests that facilitation requires a second messenger or the action of Ca2+ at a site other than that eliciting exocytosis.