Perrot-Sinal T, Ossenkopp K P, Kavaliers M
Neuroscience Programme, University of Western Ontario, London, Canada.
Psychoneuroendocrinology. 2000 Apr;25(3):259-76. doi: 10.1016/s0306-4530(99)00054-2.
Sex differences in a variety of non-reproductive behaviors have been indicated to occur in seasonally breeding polygynous promiscuous rodents such as the meadow vole, Microtus pennsylvanicus. The present study was designed to assess the effects of reproductive and hormonal status on the locomotor responses of meadow voles following brief exposure to the odors of a natural predator, the Red fox (Vulpes vulpes). Adult male and female meadow voles, which are seasonal photoperiodically-induced breeders, were housed in either mixed sex pairs under a long, reproductively stimulatory photoperiod (simulating breeding: long light cycle, paired: LLC + P) or in same-sex pairs under a short, reproductively inhibitory photoperiod (simulated non-breeding: short light cycle, non-paired: SLC-NP). On 2 consecutive days following 1 day of baseline activity monitoring, voles were exposed individually for 3 min to fox odor and a novel pungent control odor (extract of almond). The levels of various measures of activity that were displayed by the voles were assessed by an automated Digiscan activity monitoring system. LLC + P (simulated breeding) voles displayed higher basal levels of activity relative to SLC + NP (simulated non-breeding) voles, with males displaying greater activity than females. LLC + P (simulated breeding) males displayed a significant reduction in activity levels following exposure to fox odor relative to control odor. The reductions in activity following fox odor exposure were related to plasma testosterone levels such that a larger behavioral response (i.e. greater reduction) was associated with higher levels of testosterone. Furthermore, dividing males into high and low testosterone groups based on the median levels of testosterone revealed that high but not low testosterone males displayed reductions in activity following exposure to fox odor relative to control odor. No changes in activity levels following exposure to fox odor were noted in SLC-NP males, and either SLC-NP or LLC + P females. These results show that this sexually dimorphic non-reproductive behavior is significantly influenced by reproductive condition and gonadal hormone levels.
在季节性繁殖的多配偶混交啮齿动物，如草甸田鼠（Microtus pennsylvanicus）中，已表明在多种非繁殖行为上存在性别差异。本研究旨在评估繁殖和激素状态对草甸田鼠在短暂暴露于自然捕食者红狐（Vulpes vulpes）气味后的运动反应的影响。成年雄性和雌性草甸田鼠是季节性光周期诱导繁殖者，它们被饲养在长的、具有繁殖刺激作用的光周期下的混合性别对中（模拟繁殖：长光照周期，成对：LLC + P），或者被饲养在短的、具有繁殖抑制作用的光周期下的同性对中（模拟非繁殖：短光照周期，非成对：SLC - NP）。在进行1天的基线活动监测后的连续2天，田鼠被单独暴露于狐狸气味和一种新的刺激性对照气味（杏仁提取物）3分钟。通过自动Digiscan活动监测系统评估田鼠表现出的各种活动测量水平。与SLC + NP（模拟非繁殖）田鼠相比，LLC + P（模拟繁殖）田鼠表现出更高的基础活动水平，雄性比雌性表现出更大的活动量。相对于对照气味，LLC + P（模拟繁殖）雄性在暴露于狐狸气味后活动水平显著降低。暴露于狐狸气味后活动的降低与血浆睾酮水平有关，即更大的行为反应（即更大的降低）与更高的睾酮水平相关。此外，根据睾酮的中位数水平将雄性分为高睾酮组和低睾酮组，结果显示，相对于对照气味，高睾酮但非低睾酮的雄性在暴露于狐狸气味后活动降低。在SLC - NP雄性以及SLC - NP或LLC + P雌性中，未观察到暴露于狐狸气味后活动水平的变化。这些结果表明这种性别二态性的非繁殖行为受到繁殖状况和性腺激素水平的显著影响。
