A short term protocol for preclinical pharmacology studies in SOD1^G93A transgenic mice.

<p>Effects on rotarod performance are assessed between days 35 to 60, analysis of hind-limb muscle volume and immunohistochemistry to assess the degree of gastrocnemius innervation at day 60 in half of the cohort and the remaining cohort being assessed for motor function using the catwalk gait analysis system and for time to onset. The n numbers have been selected on the basis of the data presented in this paper. The most variable readout requiring the largest n is the time to reach a 20% reduction in rotarod performance with a coefficient of variation (CV) ranging from 9.0% to 26.6% and an average CV of 17%. Fourteen mice per group are required to detect a shift of 10 days in this initial decline in rotarod performance with a power of 80% (two-tailed Student's T test, α = 0.05, β = 0.8). Power analysis shows an n of 7 is sufficient to detect a 20% change in muscle volume assessed using MRI based on the 60 day data for SOD1^G93A mice shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0023244#pone-0023244-g004" target="_blank">figure 4</a>, where hind-limb muscle volume was 0.25 cm³+/−0.033 (SD) on day 60 (Student's independent T test, two-tailed, α = 0.05 and β = 0.8). From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0023244#pone-0023244-g003" target="_blank">figure 3</a> the percentage of innervated neuromuscular junctions in the gastrocnemius muscle of 60 day old SOD1^G93A transgenic mice was 37.4+/−8.5% (SD). Assuming a 15% increase in this level of innervation to 52.4%, an n of 7 per group would give 80% power (β = 0.8) at a significance level of 0.05 (Students T test, two-tailed). For onset, 7 mice per group is sufficient to detect a difference of 1 week in onset of clinical signs of disease (two-tailed Student's T test, α = 0.05, β = 0.8). All power analyses were performed with G*Power version 3.0.3.