INFLUENCE OF THE MOTHER ON DEVELOPMENT OF AGGRESSIVE-BEHAVIOR IN MALE-RATS

The present experiments investigated pre- and postnatal maternal effec ts on aggressive behavior in rats. Resident-intruder aggressive behavi or of male rats in colonies (two males and two females) was studied in five experimental groups: 1 = WWY (n = 7) the two males of each colon y were wild (biological father and mother were wild) fostered by a wil d mother; 2 = WAY (n = 11) the two males were wild fostered by an albi no Wistar mother; 3 = AAY (n = 11) the two males were albino (biologic al father and mother were Wistar) fostered by an albino mother; 4 = AW Y (n = 12) the two males were albino fostered by a wild mother; and 5 = HWX + HAX (n = 9) one of the males was hybrid born and reared by a w ild mother (the father was albino) and the other was also hybrid but b orn and reared by an albino mother (the father was wild). Each test la sted 10 min and the intruder was always a Wistar male. Aggression of w ild rats was higher than the laboratory ones, independently of the mot her (albino or wild) they were fostered by. However, hybrid males born and reared by a wild mother were more aggressive than those that were born and reared by an albino mother, in spite of the father being wil d. In conclusion, crossfostering has little effect on territorial aggr ession, but prenatal maternal effects seem to play a major role on the ontogeny of aggressive behavior of male rats.