Neuromuscular junction muscle recording

Electromyography (EMG) and nerve conduction velocities (NCVs) are used to assess the function of the peripheral nerves, neuromuscular junction, and muscles. NCVs are measured by stimulating the nerve and recording the speed of conduction of the impulse. NCVs can be used to detect the presence of localized peripheral nerve inj uries (carpal tunnel, etc.) or diffuse symmetric neuropathies (which may be inherited or acquired). EMG assesses muscle dysfunction due to primary muscle disease or secondary to nerve injury. This test is used to diagnose peripheral neuropathies (inherited and acquired), GuiUain-Barre syndrome, myasthenia gravis, amyotrophic lateral sclerosis, radiculopathies, and muscle diseases. 

Recording activity directly from the muscle fibers themselves can be clinically valuable in identifying neuromuscular disorders [19]. Therefore, invasive electrodes are needed to access the muscle fibers or the neuromuscular junction. Fine-needle electrodes or thin stainless-steel wires are inserted or implanted to obtain local recording from the fibers or neuromuscular junctions [7]. 

One of the clinical signs associated with MeHg intoxication is a myasthenia gravis-like muscle weakness in adults (Rustam et al. 1975), a syndrome which responded well to therapy with neostigmine, a reversible acetylcholinesterase inhibitor. In this syndrome, two effects of MeHg on synaptic transmission at the neuromuscular junction were demonstrated using intracellular microelectrode recording techniques (Atchison and Narahashi 1982 Atchison et al. 1984). First, nerve-evoked, synchronous quantal release of acetylcholine (ACh) is inhibited, as indicated by a decrease in end-plate potential (EPP) amplitude. Second, spontaneous quantal release... 

Figure 15.2. Drosophila larval neuromuscular junction system. A wandering third-instar larva is dissected open to reveal the ventral neuromusculature (see Figure 15.1). The peripheral nerve is severed and stimulated with a glass suction electrode. The muscle is recorded from in two-electrode voltage-clamp (TEVC) configuration. The postsynaptic excitatory junctional current (EJC) is recorded to assay synaptic transmission bottom inset). Top inset) Basis of synaptic transmission event being evoked by nerve stimulation and recorded via ion flux through muscle glutamate receptors.

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