Jimenez Jessica A, McCoy Eric S, Lee David F, Zylka Mark J
UNC Curriculum in Toxicology and Environmental Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA.
UNC Neuroscience Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA.
F1000Res. 2024 Jul 3;12:234. doi: 10.12688/f1000research.130474.3. eCollection 2023.
The open field assay is used to study anxiety-related traits and anxiolytic drugs in rodents. This assay entails measuring locomotor activity and time spent in the center of a chamber that is maintained at ambient room temperature. However, the ambient temperature in most laboratories varies daily and seasonally and can differ between buildings. We sought to evaluate how varying ambient temperature and core body temperature (CBT) affected open field locomotor activity and center time of male wild-type (WT, C57BL/6) and Transient Receptor Potential Subfamily M Member 8 ( ) knock-out ( ) mice. TRPM8 is an ion channel that detects cool temperatures and is activated by icilin.
Mice were placed in the open field at 4°C and 23°C for 1 hour. Distance traveled and time spent in the center were measured. Mice were injected with icilin, M8-B, diazepam, or saline, and changes in activity level were recorded.
The cooling agent icilin increased CBT and profoundly reduced distance traveled and center time of WT mice relative to controls. Likewise, cooling the ambient temperature to 4°C reduced distance traveled and center time of WT mice relative to mice. Conversely, the TRPM8 antagonist (M8-B) reduced CBT and increased distance traveled and center time of WT mice when tested at 4°C. The TRPM8 antagonist (M8-B) had no effect on CBT or open field behavior of mice. The anxiolytic diazepam reduced CBT in WT and mice. When tested at 4°C, diazepam increased distance traveled and center time in WT mice but did not alter open field behavior of mice.
Environmental temperature and drugs that affect CBT can influence locomotor behavior and center time in the open field assay, highlighting temperature (ambient and core) as sources of environmental and physiologic variability in this commonly used behavioral assay.
旷场试验用于研究啮齿动物的焦虑相关特质及抗焦虑药物。该试验需要测量运动活动以及在保持室温环境的实验箱中央区域所花费的时间。然而，大多数实验室的环境温度每天和季节性都会变化，不同建筑物之间也可能存在差异。我们试图评估环境温度和核心体温（CBT）的变化如何影响雄性野生型（WT，C57BL/6）和瞬时受体电位M亚家族成员8（TRPM8）基因敲除（TRPM8 -/-）小鼠的旷场运动活动和中央区域停留时间。TRPM8是一种能检测低温并被依西利定激活的离子通道。
将小鼠置于4°C和23°C的旷场环境中1小时。测量小鼠的移动距离和在中央区域停留的时间。给小鼠注射依西利定、M8 - B、地西泮或生理盐水，并记录活动水平的变化。
降温剂依西利定使CBT升高，并使野生型小鼠的移动距离和中央区域停留时间相对于对照组大幅减少。同样，将环境温度降至4°C时，野生型小鼠的移动距离和中央区域停留时间相对于TRPM8 -/-小鼠减少。相反，在4°C测试时，TRPM8拮抗剂（M8 - B）降低了CBT，并增加了野生型小鼠的移动距离和中央区域停留时间。TRPM8拮抗剂（M8 - B）对TRPM8 -/-小鼠的CBT或旷场行为没有影响。抗焦虑药物地西泮降低了野生型和TRPM8 -/-小鼠的CBT。在4°C测试时，地西泮增加了野生型小鼠的移动距离和中央区域停留时间，但未改变TRPM8 -/-小鼠的旷场行为。
影响CBT的环境温度和药物可在旷场试验中影响运动行为和中央区域停留时间，突出了温度（环境温度和核心体温）作为这种常用行为试验中环境和生理变异性的来源。
