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

1198 Words May 7th, 2013 5 Pages
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
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A typical experiment began by performing a “TRAINS” experiment with a fresh preparation in the chamber containing normal Ringer’s solution; 6 trains were recorded, each at a different CT interval, in the sequence as indicated above. OUR PRIMARY PUROSE WAS TO OBSERVE INCREASES IN SYNAPTIC EFFICACY, I.E., T/C RATIOS >> UNITY. In order to achieve this purpose, SYNAPTIC FATIGUE was induced immediately following the control measurements. This was accomplished by continuous stimulation of the nerve at 0.15-3.0 Hz for a period 10-50 min, depending on the season. In most experiments, curare was present while the preparation was being fatigued. The KEY procedure is the continuous stimulation of the nerve (Fig.5). Curare seems to intensify the increased synaptic efficacy brought about by the synaptic fatigue and to stabilize the preparation. Once the twitch is lowered by 85-95%, the TRAINS experiment is repeated in order to obtain experimental data.

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CALCULATION OF THE ! T/C RATIO! Using LabScribe software and with reference to Fig. 2, one cursor is placed on b (baseline) and the other one is placed on c (C peak); the voltage difference between the cursors is taken as the amplitude of the C twitch at its PEAK. Then, without moving the cursor on point b, the second cursor is placed on t (T peak); the voltage difference between the cursors is taken as the amplitude of the T twitch at its PEAK.

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