Fig. 11.

Colorectal motility is abnormal in SERT −/− mice. A, SERT +/+ and −/− littermates are compared with respect to body weight, the wet weight of stools (per 24 hr), and the water content of the 24 hr stools. Note that the mice do not differ with respect to body weight, but that the SERT −/− animals excrete heavier stools that contain more water than those of their SERT +/+ littermates. B, C, Histograms and corresponding z scores are shown for the distributions of time to expulsion of a glass bead placed into the colon 2 cm from the anal verge. Note that the distribution of expulsion times approximates that of a normal distribution in SERT +/+ mice (B) but is highly skewed in SERT −/− animals (C). Most of the expulsion times of the SERT −/− mice are shorter than those of controls, but the expulsion times are highly prolonged in a small subset of the animals. D, The mean expulsion times for the glass beads are compared between the SERT +/+ mice and the two groups of SERT −/− animals, one with diarrhea and one with constipation. Expulsion times of the SERT −/− mice with diarrhea are significantly faster than those of SERT +/+ mice, whereas those of constipated mice are significantly longer.