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Purpose of the study Nerve-muscle physiology is a very basic and vital module in undergraduate physiologycurriculum. The practical sessions on this system are demonstrated on amphibian (frog) nerve-musclepreparation, which becomes a limiting factor in most of the medical colleges of India. In this study, wepropose an alternative approach by using mammalian (rat) model for nerve-muscle physiology undergraduatepractical experiments.Materials and

methods:

Rat in-situ sciatic nerve-soleus muscle preparation was used to study neuromusculartransmission. Stimulation of nerve and recording of muscle contraction (force) were done by using digitalrecording system. To demonstrate fatigue, repetitive electrical stimulation was applied to nerve-musclepreparation and muscle twitches were recorded. A reduction in amplitude of contraction to 50% of their basalrecording was considered as onset of fatigue. To demonstrate site of fatigue, the muscle was stimulateddirectly after the fatigue was observed with nerve stimulation and muscle twitch recorded. To observe theeffect of neuromuscular blocking drug Pancuronium bromide, on neuromuscular transmission, in a separateset up the drug was injected in muscle belly at multiple sites and nerve was stimulated to elicit muscletwitch. The response (amplitude of muscle twitch) was compared with control (injection of 0.9% saline).Main

findings:

On repeated stimulation of nerve muscle preparation, initially there was an increase inamplitude of contraction but progressively amplitude went on decreasing. After development of fatigue ondirect muscle stimulation, amplitude recorded was same as the initial twitch amplitude. This demonstratesthat the site of fatigue is not the muscle. Further, as nerve is also non- fatigable, site of fatigue wasneuromuscular junction.Injection of Pancuronium bromide showed that the twitch amplitude decreased substantially than the control(saline injection) on stimulation of nerve, but on direct muscle stimulation amplitude of contraction remainedsame as initial, confirming the effect of drug on neuromuscular junction.