Giovenardi Marcia, de Azevedo Marcia S, da Silva Simone P, Hermel Erica do E S, Gomes Carmen M, Lucion Aldo B
Laboratório de Neurociências, Universidade do Vale do Rio dos Sinos, São Leopoldo, Brazil.
Physiol Behav. 2005 Sep 15;86(1-2):209-17. doi: 10.1016/j.physbeh.2005.07.011.
Neonatal handling reduces fear in male and cycling female rats, but increases maternal aggressive behavior against intruders to the nest area. Present study aimed to analyze the effects of neonatal handling on the maternal aggressive behavior and the activity in the open field with a predator of lactating rats on the 8th and the 18th postpartum days (periods of high and low aggressiveness). As pups, animals were divided into two groups: nonhandled (no neonatal manipulation) and handled (handling for 1 min during the first 10 days after delivery). As adults, females of both groups were impregnated and tested against a male intruder for aggressive behavior and in the open field with a cat inside a wire-meshed cage. Results showed that on the 8th day frequency of aggressive behaviors of handled females was higher than that of the nonhandled ones, but on the 18th day, no significant difference was detected. Surprisingly, in the open field test, handled females showed decreased locomotion and increased freezing on the 8th day compared to the nonhandled ones. The opposite relationship between increased aggressiveness with reduced fear is observed in the nonhandled control females in early and late lactation periods. However, neonatal handling abolishes this relationship. Apparently, the increased aggressiveness in neonatal handled lactating females does not depend on a decrease in fear. Our findings support the hypothesis that long lasting effects of early life stimulation is a dynamic function depending on the behavioral system and the period of life analyzed. Moreover, they caution the relationship between aggressive behavior and fear.
新生期处理可降低雄性和处于发情周期的雌性大鼠的恐惧，但会增加母鼠对侵入巢穴区域的入侵者的攻击性行为。本研究旨在分析新生期处理对产后第8天和第18天（攻击性高低不同的时期）哺乳期大鼠针对入侵者的母性攻击行为及旷场活动的影响。幼崽期时，动物被分为两组：未处理组（无新生期操作）和处理组（分娩后前10天每天处理1分钟）。成年后，两组雌性大鼠受孕，并针对雄性入侵者测试其攻击行为，同时在有猫的金属丝网笼内的旷场中进行测试。结果显示，在第8天，处理组雌性大鼠的攻击行为频率高于未处理组，但在第18天，未检测到显著差异。令人惊讶的是，在旷场试验中，与未处理组相比，处理组雌性大鼠在第8天的活动减少且僵住行为增加。在未处理的对照雌性大鼠的早期和晚期哺乳期，观察到攻击性增加与恐惧减少之间存在相反的关系。然而，新生期处理消除了这种关系。显然，新生期处理的哺乳期雌性大鼠攻击性增加并不依赖于恐惧的减少。我们的研究结果支持这样的假设，即早期生活刺激的长期影响是一种动态功能，取决于行为系统和所分析的生命阶段。此外，它们警示了攻击行为与恐惧之间的关系。
