In the SOD1G93A mice, GDNF mRNA expression in the hindlimb muscles is indetectable at the presymptomatic stage, increases by the onset of motor symptoms and continues with a marked decrease overtime, while in ALS patients GDNF mRNA expression tends to reduce in advanced muscle pathology, and the serum levels of GDNF are markedly lower in ALS patients than in healthy subjects38–40. This evidence concerns the gene GDNF and amyotrophic lateral sclerosis.