[Effects of morphine on the successive generation]

The preference and physical dependence for morphine, changes in gross behaviors and growth were investigated in the offspring of pregnant rats treated with morphine. Six groups (A-F) of the pregnant rats were treated with morphine by DAF (drug-admixed food) method for the following periods. No morphine-treatment was received in group A, treatment form the beginning of pregnancy (day 0) to weaning in group B, from day 0 to day 14 in group C, from day 15 to day 21 in group D, from day 0 to weaning in group E (the same of B), and no treatment in group F. The pups of group E were fostered to maters of group F, and pups of group F, and pups of group F were to maters of group E. The preference rate for morphine in pregnant rats increased significantly in comparison with of non-pregnant rats. Weanling rates of group B, C, D and E decreased significantly when compared with that of group A. The pups of maternal rats treated with morphine showed hyperactivity and vocalization. These symptoms were considered to be resulted from the withdrawal signs. The withdrawal signs may produce the decrease in the weanling rates. There was no difference in body weight gains in the offspring between group A and B. Preference rate for morphine in the offspring of group B was lower than that of group A. It may be due to an enhanced susceptibility to morphine in group B. However, no marked change in intensity of physical dependence on morphine was detected in the offspring between group A and B.