*2.10. Statistics*

Results are expressed as mean ± SEM. SPSS 15.0 (SPSS Inc., Chicago, IL, USA) and GraphPad Prism 5.0 (GraphPad Software Inc., San Diego, CA, USA) software were used. A 2 × 2 factorial design with multivariate general lineal model analysis evaluated genotype (G) and sex (S) effects. Two independent groups were compared with Student's *t*-test, while comparisons for related samples were made with the paired *t*-test. The survival curve was analyzed with the Kaplan–Meier test. Relaxations to ACh and sodium nitroprusside were expressed as the percentage change from the Phe precontracted level. Contractions to Phe are expressed as a percentage of the tone generated by 100 mM KCl. The area under the curve was individually calculated from each concentration–response curve to ACh, sodium nitroprusside, and Phe and was expressed as arbitrary units. Differences between concentration–response curves were assessed by two-way repeated measures ANOVA with Tukey's post-test. The correlations between the different variables studied were evaluated with Pearson's correlation. In all the tests, *p* < 0.05 was considered statistically significant.

#### **3. Results**
