Exposure to ethanol during pregnancy in mice: potential importance of dose for the development of tolerance in offspring.

CD-1 albino mice were given Portagen-10 percent ethanol (ETOH) or isocaloric Portagen-sucrose during pregnancy to determine if tolerance developed in utero and to describe the temporal pattern of its decline postnatally. ETOH mothers did not significantly increase their consumption of ETOH but gained in body weight during pregnancy, showed no signs in the open field of withdrawal from ETOH shortly after delivery and showed less pup-caring behavior than pair-fed controls (PFC). Among offspring 1, 3, 10, 25 and 60 days old, only 25-day old ETOH pups metabolized and cleared an anesthetic dose of ETOH more efficiently than PFC animals, suggesting the absence of Dispositional Tolerance in the other animals. PFC offspring 10 days old took significantly longer to lose the righting reflex than their ETOH counterparts following the anesthetic dose of ETOH, the difference being opposite that which would suggest the occurrence of Adaptive Tolerance. Data are discussed primarily in terms of decreases in dose of ETOH to which mothers and fetuses were exposed during pregnancy.