ECG at end stages of G418 toxicity. ECGs were recorded in mice of unaffected genotypes at advanced stages of G418 toxicity, along with littermate saline controls. A) Body mass of G418 and saline injected mice. B) Heart rates and (C) PR intervals were affected by G418 toxicity. D) QRS interval was not significantly affected by toxicity. E–F) Measures of heart rate variability, reflecting autonomic nerve control of the heart, were not affected by toxicity. (n of 4, ages range from PND19 to PND23, * P less than 0.0.5)