RESUMO
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.
RESUMO
Purpose of the study: Physiology practical complement learning of concepts taught in didactic theorylectures. Therefore, they are instrumental to comprehensive learning. Learning of physiology of excitabletissues is supplemented by observing the same phenomena in action in the laboratory. We developed anin-situ rat nerve-muscle model to demonstrate nerve-muscle physiology phenomenon to undergraduate andpostgraduate students. This mimics the physiological conditions unlike the Rana tigrina experiments whichwere done earlier. Further, frequent unavailability of frogs envisaged us to find an alternative for demonstrationof these concepts.Materials and methods: We developed and standardized an in-situ rat soleus muscle-sciatic nerve modelto demonstrate the phenomenon of nerve-muscle properties like simple muscle twitch, effect of strength ofstimulus, effect of two successive stimuli and tetanus to the undergraduate and postgraduate students atour institute.Results: Simple muscle twitch was recorded and effect of increasing strength of stimuli was observed.Thereafter, effect of two successive stimuli and genesis of tetanus was recorded in the same experimentalset up. We successfully standardised this in-situ model for teaching nerve and muscle physiology to our students.Conclusion: We propose an easy and effective experimental rat in-situ model for nerve-muscle physiologyteaching to students