Abstract
A devastating earthquake and tsunami hit Japan on March 11, 2011, followed by several long and intense aftershocks. Laboratory mice housed in the Tokyo, located approximately 330 km south of this earthquake’s epicenter, displayed remarkable changes in a variety of behaviors and physiological measures. Although unusual pre-earthquake behaviors have been previously reported in laboratory animals, little is known about behavioral and physiological changes that occur after a great earthquake. In the present study, the effects of Tohoku earthquake on mice behavior were investigated. “Earthquake-experienced” mice displayed a marked increase in food consumption without gaining body weight in response to the earthquake. They also displayed enhanced anxiety, and in a formal fear memory task, showed significantly greater tone- and context-dependent conditioned freezing. Water maze performance of earthquake-experienced mice showed the quicker acquisition of the task, faster swim speed and longer swim distance than the naive mice. Serum corticosterone levels were elevated compared to the naive mice, indicating that the earthquake and aftershocks were stressful for the mice. These results demonstrate that great earthquakes strongly affect mouse behaviors and physiology. Although the effects of a variety of experimental manipulations on mouse behaviors in disease models or in models of higher cognitive functions have been extensively examined, researchers need to be aware how natural phenomena, such as earthquakes and perhaps other natural environmental factors, influence laboratory animal behaviors and physiology.
Highlights
Rodents are the most widely used animal research subjects, comprising about 95% of all laboratory animals used in scientific research [1]
A major seismic event measuring intensity 5-upper on the Japanese Meteorological Agency (JMA) seismic intensity scale occurred on March 11, 2011, followed by numerous aftershocks (Figure 1A; data relating to the earthquake were obtained from Japan Meteorological Agency)
Alteration of dissolved organic compounds in the water has been considered to function as the seismic precursor in the wild animals [4], apparent changes were not detected in chemical component of water sampled at three time points from October 2010 to May 2011 (Table 2; data relating to the water chemistry were obtained from the Bureau of Waterworks, Tokyo Metropolitan Government) to cover the data for before or after the earthquake
Summary
Rodents are the most widely used animal research subjects, comprising about 95% of all laboratory animals used in scientific research [1]. Among the several kinds of geophysical variations that occur before earthquakes, the altered magnetic fields precursor may account for abnormal behaviors in laboratory mice [5]. In spite of such pre-earthquake studies, little is known about the behavioral changes that occur after earthquakes. Previous research has demonstrated that earthquakes increase the prevalence of psychiatric distresses such as depression and anxiety in humans [8]. Taken together, these results led us to hypothesize that earthquakes may influence an aspect of behaviors in laboratory animals
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