Twin-Pulse Facilitation Measured as Twitch Ratios in the Frog Sciatic Nerve/Gastrocnemius Muscle Preparation

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Twin-Pulse Facilitation Measured as Twitch Ratios at the! Frog Nerve/Gastrocnemius Preparation ! Richard S. Manalis and Jonathan L. Miller— Department of Biology, Goshen College, Goshen, Indiana Introduction! Learning & Memory are related to synaptic efficacy which the present study brings to the undergraduate physiology laboratory. TWIN-PULSE FACILITATION has been widely used to study one aspect of short-term synaptic plasticity at a wide variety of synapses using electrophysiological methods. Here we show that measurements of muscle twitches from the easily prepared sciatic nerve/gastrocnemius preparation of the frog can allow one to perform experiments involving TWIN-PULSE FACILITATION. The advantages of measuring muscle twitches…show more content…
Fig. 5. SYNAPTIC FATIGUE (depression) was induced by stimulating the nerve at 0.15 Hz for 48 min. 2.3 μM curare was also present. The twitch was reduced by 95% as a result.! ------------------------------------------! Materials and Methods! Results! Fig. 6. This is a typical record from an experiment in which a train of 5 identical dual-pulses were applied to the nerve. The CT interval for the above recording was 120 ms; Fig. 2B was taken from a portion of this record, specifically, the twitches produced by the 5th stimulus. In the actual experiment, a series of trains were applied. There was a 2 min rest between trains, and each train corresponded to a different CT interval.! !Visual inspection of the 5 sequential contractions suggests a !dynamic interplay of factors affecting transmitter release: !! !!The conditioning twitches trend downward, indicating ! !depression.! !!Concomitantly, the test twitches trend upward, as do the ! !resultant T/C ratios, indicating facilitation.! !Control measurements, using the same series of stimulus !trains, revealed T/C ratios that were close to unity. ! ! !! Using relatively simple muscle twitch measurements, we have observed increases in synaptic efficacy in frog sciatic nerve/ gastrocnemius muscles that have undergone synaptic fatigue in the presence of curare. A new stimulus protocol is described in which

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