Weil Zachary M, Bowers Stephanie L, Dow Eliot R, Nelson Randy J
Departments of Neuroscience and Psychology, and Institute of Behavioral Medicine Research, The Ohio State University, Columbus, OH 43210, USA.
Physiol Behav. 2006 Apr 15;87(4):694-9. doi: 10.1016/j.physbeh.2006.01.005. Epub 2006 Feb 20.
Lactating females direct aggressive behaviors towards intruders presumably to reduce the likelihood of infanticide of their pups. Infected animals display a constellation of responses that include lethargy, anorexia, and decreased social interactions. This suite of responses is referred to as sickness behavior, and is putatively part of an adaptive strategy to aid the organism in recovery from infection. Previous work has suggested that animals can suppress the behavioral symptoms of sickness in order to engage in adaptive behaviors. To test whether adaptive nest defense is affected by illness, dams received a peripheral injection of either saline or lipopolysaccharide (LPS [50, 400, or 1000 microg/kg]), a non-replicating component of bacterial cell walls that activates the immune system. Simulated infection with LPS reduced body mass and food intake in dams and interfered with litter growth in a dose-dependent manner. Generally, nest defense was unaffected by LPS; the proportion of dams displaying maternal aggression against a male intruder, as well as the latency and duration of aggressive encounters were only suppressed at the highest LPS dose tested. Further, LPS treatment also altered non-agonistic behavior during the aggression test as indicated by reduced social investigation of the intruder and an increased time spent immobile during the session. LPS administration also significantly increased serum corticosterone concentrations in lactating females. These findings suggest that maternal aggression is not suppressed by LPS-evoked immune activation at doses that attenuate other aspects of maternal and social behavior.
哺乳期雌性会对入侵者表现出攻击行为，大概是为了降低幼崽被杀害的可能性。受感染的动物会表现出一系列反应，包括嗜睡、厌食和社交互动减少。这一系列反应被称为疾病行为，据推测是一种适应性策略的一部分，有助于生物体从感染中恢复。先前的研究表明，动物可以抑制疾病的行为症状以参与适应性行为。为了测试适应性筑巢防御是否受疾病影响，给母鼠进行外周注射生理盐水或脂多糖（LPS [50、400或1000微克/千克]），脂多糖是细菌细胞壁的一种非复制成分，可激活免疫系统。用LPS模拟感染会降低母鼠的体重和食物摄入量，并以剂量依赖的方式干扰幼崽生长。一般来说，筑巢防御不受LPS影响；对雄性入侵者表现出母性攻击行为的母鼠比例，以及攻击遭遇的潜伏期和持续时间，仅在测试的最高LPS剂量下受到抑制。此外，如侵略测试期间对入侵者的社交调查减少以及静止不动时间增加所示，LPS处理也改变了非攻击性的行为。LPS给药还显著提高了哺乳期雌性的血清皮质酮浓度。这些发现表明，在减弱母性和社会行为其他方面的剂量下，LPS诱发的免疫激活不会抑制母性攻击行为。
