EFFECTS OF EMBRYO-TRANSFER AND CORTICAL ECTOPIAS UPON THE BEHAVIOR OFBXSB-YAA AND BXSB-YAA PLUS MICE

The BXSB-Yaa and BXSB-Yaa + inbred strains of mice differ primarily wi th respect to the Y chromosome, although there is evidence that they d iffer on several autosomal genes as well. Each strain has ectopic coll ections of neurons in neocortical layer I (ectopias), with a higher oc currence in males (58%) than females (42%). Conventionally reared mice from these strains were compared to mice that were transferred, as 8- cell embryos, into the uteri of non-autoimmune recipients, who gave bi rth to and reared the offspring. The transfer procedure did not change the incidence of ectopias in either sex. There were, however, major d ifferences in behavior. Compared to conventionally reared controls, em bryo transfer mice had greater behavioral asymmetry, poorer performanc e in a black-white discrimination, poorer Morris maze learning, batter Lashley maze learning, and better performance in a two-way shuttlebox . Within the transfer groups, females differed as much as males, confi rming our prior findings and supporting our thesis that the two strain s differ on several autosomal genes in addition to the Y chromosome. T hese findings show that the intra-uterine environment can powerfully a nd selectively affect later behavior. When ectopic and non-ectopic mic e were compared, BXSB-Yaa mice with neocortical ectopias were better a ble to learn the Morris spatial maze than non-ectopic controls; this w as true whether the mice were conventionally reared or embryo transfer red. In contrast, BXSB-Yaa + ectopic mice did not differ from their co ntrols if conventionally reared, but were much worse than controls if embryo transferred.