PMC5650981_01
Repetitive nerve stimulation at the time of initial evaluation. Repetitive stimulation of the tibial nerve performed before (A) and after (B) intravenous administration of edrophonium chloride (0.1 mg/kg). Nerve stimulation was performed at the level of the hock, and complex muscle action potentials (CMAP) were recorded from the interosseous muscle. Stimulus rate = 2 Hz. Stimulus duration = 0.1 ms. Repetitions = 10. Normal response = no decrement >10% of the starting CMAP amplitude or area. (A) Repetitive nerve stimulation prior to administration of edrophonium chloride showed a decrement of 74% between the first and fifth waves. (B) Repetitive nerve stimulation after administration of edrophonium chloride showed a persistent but less severe decrement of 37% between the first and fifth waves.
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F1
Repetitive stimulation of the tibial nerve at the level of the hock with a stimulus rate of 2 Hz revealed a decrement in compound muscle action potential (CMAP) amplitude of 74% between the first and fifth waves (Figure 1A). Repetitive nerve stimulation following administration of edrophonium (0.1 mg/kg, IV) using the same stimulus parameters showed a persistent but improved decrement in CMAP amplitude of 37% between the first and fifth waves (Figure 1B).
Localization of motor end-plates and acetylcholine receptors (AChRs) in external intercostal muscle of a dog with congenital myasthenic syndrome (CMS). End-plate AChRs were non-detectable using immunofluorescent staining of cryosections of the external intercostal muscle in the affected CMS dog and stained appropriately in control sections. Cryosections from the affected dog and control archived tissue were reacted for esterase to identify neuromuscular junctions. Serial sections were reacted with labeled alpha-bungarotoxin (alpha-bgt) for identification of AChRs (highlighted in red). End-plates are noted with arrows in both the affected and control muscles. End-plates are present in the muscle from the CMS dog but AChRs are not found.
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F2
Compared to archived control muscle, motor end-plates were identified but AChRs were undetectable (Figure 2) further supporting a diagnosis of CMS.