Morphological analysis of neuromuscular junction development and degeneration in rodent lumbrical muscles.

BACKGROUND: The neuromuscular junction (NMJ) is a specialised synapse formed between a lower motor neuron and a skeletal muscle fibre, and is an early pathological target in numerous nervous system disorders, including amyotrophic lateral sclerosis (ALS), Charcot-Marie-Tooth disease (CMT), and spinal muscular atrophy (SMA). Being able to accurately visualise and quantitatively characterise the NMJ in rodent models of neurological conditions, particularly during the early stages of disease, is thus of clear importance. NEW METHOD: We present a method for dissection of rodent deep lumbrical muscles located in the hind-paw, and describe how to perform immunofluorescent morphological analysis of their NMJs. RESULTS: These techniques allow the temporal assessment of a number of developmental and pathological NMJ phenotypes in lumbrical muscles. COMPARISON WITH EXISTING METHODS: Small muscles, such as the distal hind-limb lumbrical muscles, possess a major advantage over larger muscles, such as gastrocnemius, in that they can be whole-mounted and the entire innervation pattern visualised. This reduces preparation time and ambiguity when evaluating important neuromuscular phenotypes. CONCLUSIONS: Together, these methods will allow the reader to perform a detailed and accurate analysis of the neuromuscular system in rodent models of disease in order to identify pertinent features of neuropathology.