Giovenardi M, Consiglio A R, Barros H M, Lucion A B
Departamento de Fisiologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brasil.
Braz J Med Biol Res. 2000 Sep;33(9):1083-8. doi: 10.1590/s0100-879x2000000900015.
High levels of aggressive behaviors against intruders in the nest area are displayed by female rats during the first 10 days after delivery, declining thereafter to very low levels, even though lactation continues. Cross-fostering experiments were undertaken to test the hypothesis that pup age may affect aggression in lactating rats. The behavior of females on the 8th day after delivery when raising fostered 8-day-old pups was compared to that of females on the 8th postpartum day raising older pups (18 days old) for the last 5 days, and females on the 18th day after delivery raising fostered 18-day-old pups were compared to females in the same postpartum period nursing younger pups (8 days of age at the time of the maternal aggression test) for 5 days. Pup retrieval activity and plasma prolactin level were also analyzed. Females on the 8th postpartum day nursing 18-day-old pups were less aggressive than females in the same postpartum period, but with 8-day-old pups. Likewise, females on the 18th postpartum day nursing younger pups were more aggressive and presented higher levels of prolactin than females nursing older pups. Thus, pup development can alter the natural decline of maternal aggressive behavior.
分娩后的头10天里，雌性大鼠会对巢穴区域内的入侵者表现出高度的攻击行为，此后这种行为会降至极低水平，即便哺乳期仍在继续。进行了交叉寄养实验，以检验幼崽年龄可能影响哺乳期大鼠攻击性的假设。将分娩后第8天养育寄养8日龄幼崽的雌性大鼠的行为，与产后第8天养育较大幼崽（18日龄）达5天的雌性大鼠的行为进行比较，并且将分娩后第18天养育寄养18日龄幼崽的雌性大鼠，与在同一产后时期养育较年幼幼崽（在母体攻击性测试时8日龄）达5天的雌性大鼠进行比较。还分析了幼崽找回活动和血浆催乳素水平。产后第8天养育18日龄幼崽的雌性大鼠，比同一产后时期养育8日龄幼崽的雌性大鼠攻击性更低。同样，产后第18天养育较年幼幼崽的雌性大鼠，比养育较大幼崽的雌性大鼠攻击性更强，且催乳素水平更高。因此，幼崽发育会改变母体攻击行为的自然下降趋势。
