Measuring Neuromuscular Junction Functionality in the SOD1(G93A) Animal Model of Amyotrophic Lateral Sclerosis.

Emanuele Rizzuto,Antonio Musarò,Zaccaria Del Prete,Simona Pisu

doi:10.1007/s10439-015-1259-x

Abstract

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that leads to motor neuron degeneration, alteration in neuromuscular junctions (NMJs), muscle atrophy, and paralysis. To investigate the NMJ functionality in ALS we tested, in vitro, two innervated muscle types excised from SOD1G93A transgenic mice at the end-stage of the disease: the Soleus, a postural muscle almost completely paralyzed at that stage, and the diaphragm, which, on the contrary, is functional until death. To this aim we employed an experimental protocol that combined two types of electrical stimulation: the direct stimulation and the stimulation through the nerve. The technique we applied allowed us to determine the relevance of NMJ functionality separately from muscle contractile properties in SOD1G93A animal model. Functional measurements revealed that the muscle contractility of transgenic diaphragms is almost unaltered in comparison to control muscles, while transgenic Soleus muscles were severely compromised. In contrast, when stimulated via the nerve, both transgenic muscle types showed a strong decrease of the contraction force, a slowing down of the kinetic parameters, as well as alterations in the neurotransmission failure parameter. All together, these results confirm a severely impaired functionality in the SOD1G93A neuromuscular junctions.

Highlights

Amyotrophic lateral sclerosis (ALS) is a disease that leads to motor neuron degeneration, muscle atrophy and paralysis.[23,43] different pathogenicAddress correspondence to Emanuele Rizzuto, Department of Mechanical and Aerospace Engineering, Sapienza University of Rome, 00184 Rome, Italy
Length and estimated Cross Sectional Area (CSA) are reported in Table 1 for SOD1G93A and wild-type C57BL/6 (WT) Soleus
SOD1G93A muscles had a lower rate of force generation, dF/dt (Fig. 2c), and dF/dt was even smaller with nerve stimulation than with direct stimulation

Summary

Introduction

Previous studies on SOD1G93A mice reported a deficit of the extensor digitorum longus (EDL) in generating maximum force after the onset of the pathology[12,24] and a trend toward lower values of maximum specific force in diaphragm strips,[24] when compared to wild type littermates. Those studies did not determine whether the alterations were due to changes either in muscle or in neuromuscular transmission. The diaphragm is functional until death, usually caused by diaphragmatic failure and hypoventilation in both animal models and human patients.[17]

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