FIGURE 2.

Transient β₂-AR activation before but not after embryo attachment caused compromised pregnancy. A, representative pictures of day 12 mouse uteri after treatment of β₂-AR drugs on days 4 and 5. Red arrow shows resorption sites. Histological examination of crowded implantation sites reveals different degrees of retarded embryo growth. Illustration of a triplet shows three embryos with different developing stages in one placenta. agon, agonist; anta, antagonist. B, embryo resorption rate at day 12 (D12) of pregnancy (NS, p > 0.05, ***, p < 0.00005). C, average implantation site weight at day 12 of pregnancy (NS, p > 0.05, *, p = 0.0287, **, p = 0.0003). D, average weight of surviving embryos (NS, p > 0.05, *, p = 0.0013). E, average litter size at birth (NS, p > 0.05, **, p = 0.0004, ***, p < 0.00001). t test, error bars represent S.E. Numbers within bars indicate the number of mice examined.