This report compiles the results of a series of studies on the Tsukuba High- and Low-Emotional strains (THE and TLE) of rats (Rattus norvegicus) established at the University of Tsukuba, Japan. The THE and TLE strains have been selected, respectively, for low and high activity in a runway test. During the course of selection, defecation has increased in the THE strain and decreased in the TLE strain. These strain differences were not affected by maternal influences, early experience, or psychotropic drugs. THE rats were consistently inactive in all novel situations examined, while TLEs were very active. The level of spontaneous activity, however, was similar between the two strains. It was remarkable that THE rats showed more burrowing activity than TLE animals, whereas the latter displayed more aggression than the former. Differences in learning ability, concentration of neural transmitters, and social behavior were examined.
Tsukuba High- and Low-Emotional rats (THE and TLE), Wistar-Imamichi/Iar rats (control group for the Tsukuba Emotional rats), and F344/DuCrj rats were tested in three types of novel situations: the open field, a runway devised as a type of open field with a shelter, and an I-maze devised as a narrow runway with shelters and covers to remove rats' freezing behavior against predatory attack. The TLE was the most active, and the THE the least active in the three tests. While the F344 was inactive in the runway and the I-maze, this strain was as active as the Wistar-Imamichi in the open field. While the THE and F344 defecated frequently, the TLE never defecated.
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