Statistical Analysis
Histograms and q-q plots were used to evaluate the assumption of
normality. Continuous data were presented as mean (SD). The independent
samples Student’s t-test was used to evaluate the differences between
two groups, whilst the one-way ANOVA was used to evaluate differences
among >2 experimental groups followed by Tukey’s multiple
comparisons test. To examine the effect of genotype on tension over
extended U46619 concentrations we fitted mixed-effects models,
implementing the restriction maximum likelihood estimation, with random
intercepts for the different mice. Interactions of the genotype with the
different levels of concentration were tested. To decide upon the
inclusion of the interaction term we used the Bayesian information
criterion (BIC). The interaction term was kept in the model if it
produced a smaller BIC value compared to a model with no interaction
term. For the models with the interaction term this meant that the
genotype effect on vessel tension was not always constant, therefore it
varied according to the levels of the U46619 concentration (i.e.,
dependent of vasoconstrictor concentration: Fig. 5C, 6A, 6B, 6C & 6D).
For the models with no interaction term this meant that the genotype
effect on vessel tension was independent on the vasoconstrictor
concentration (Fig. 5A, 5B, 5D & SF. 10 E). Point estimates are stated
in text, whilst the 95% confidence intervals (95% CI) are plotted in
the relevant figures. In all analyses, the significance level was set at
5%. Data were analysed using Prism software (GraphPad version 8.1.2.,
GraphPad Software Inc.) and Stata 16 (StataCorp, 2019. Stata Statistical
Software: Release 16. College Station, TX: StataCorp LLC.).