Fig. 4.

Breathing abnormalities. a, b Abnormal breathing activity including apnea and irregular breathing was observed in Mecp2 ^−/Y rats at P35 and P81. c, d Apnea rate and respiratory frequency variation were significantly more in Mecp2 ^−/Y rats than in the WT (***P < 0.001, **P < 0.01, *P < 0.05; Student’s t test). e–h the breathing abnormalities were compared between mouse and rat (***P < 0.001; Student’s t test). g The apnea rate of Mecp2 ^−/Y rats was significantly lower than that of the Mecp2 ^−/Y mice after data normalization to the WT levels. h The severity of breathing frequency variation was not significantly different between rats and mice