This confirms your Indiana Academy of Abstract Submission for the Event ‘130th Annual Academy Meeting’. Abstract submission is below:
Muscle Twitches from Frog Muscle Used to Study Short-Term Synaptic Plasticity from a Population Perspective
Authors and Institutions:
MANALIS, Richard S., Goshen College, Goshen, IN
Short-term synaptic plasticity was studied from a population perspective; the muscle twitch, recorded from the frog (Rana pipiens) sciatic nerve/gastrocnemius muscle preparation, was the population measurement. Muscle twitches are dependent on changes in the recruitment of muscle fibers; such changes result from synaptic plasticity changes. The high safety factor of neuromuscular transmission was reduced through the continuous stimulation of the sciatic nerve at a frequency of 0.25-0.45 Hz for 25-30 min. The muscle twitch was, thereby, reduced by 85-90%, leaving the majority of the synapses in a subthreshold state or subliminal fringe. A paired-pulse facilitation protocol in which 2 stimuli are applied to the nerve at a given interval was used to study facilitation. The nerve was stimulated with trains of 5 identical paired-pulses with 2 min rests between trains. In a given train, however, the 5 contractile responses were NOT IDENTICAL. There was a sharp decay of the twitches produced by the 1st stimulus in each of the 5 paired-pulses; this illustrated depression, which is attributed to a depletion of the readily releasable pool (RRP) of synaptic vesicles. The twitches produced by the 2nd stimulus either decayed at a slower rate or actually increased during the train; this illustrated facilitation. The RRP was replenished during the subsequent 2 min rest only to be depleted again with the next train. Facilitation occurs when muscle fibers transfer from the subliminal fringe into the excited state; this is indicated when the peak of the 2nd twitch > that of the1st. The level of facilitation is inversely proportional to the interval between the two stimuli. Facilitation is readily observed at intervals >> 20 ms, which is the duration of the endplate potential. Therefore, facilitation is primarily due to an increased transmitter release at long intervals. This is the first study in which synaptic plasticity has been studied using population responses rather than single-unit responses (endplate potentials).