The open-field test is a commonly used apparatus in many behavioral studies. However, in most studies, temporal changes of details of behavior have been ignored. We thus examined open-field behavior as measured by both conventional indices and 12 ethograms supported by detailed temporal observation. To obtain a broader understanding, we used genetically diverse mouse strains: 10 wild-derived mouse strains (PGN2, BFM/2, HMI, CAST/Ei, NJL, BLG2, CHD, SWN, KJR, MSM), one strain derived from the so-called fancy mouse (JFI), and one standard laboratory strain, C57BL/6. Conventional measurements revealed a variety of relationships: some strains did not show the hypothesized association between high ambulation, longer stay in the central area, and low defecation. Our ethological approach revealed that some behaviors, such as freezing and jumping, were not observed in C57BL/6 but were seen in some wild-derived strains. Principal component analysis which included temporal information indicated that these strains had varied temporal patterns of habituation to novelty.

The present paper evaluates the inclusion of a standard strain or outbred stock in multi-strain behavioral phenotyping protocols to perform the same role as the external standard in biochemical assay procedures. As potential standards, the F344 inbred strain and an outbred stock of Long Evans were tested with three other inbred strains. To evaluate the influence of rearing conditions on phenotype stability, one group of F344s was born at the University of Tsukuba, another, bred elsewhere and delivered to Tsukuba at 4 weeks of age. All animals were tested in open-field (OF), runway emergence (RE) and digging tests as adults. The results showed no influence of breeding or transportation history on OF and RE behavior of the two F344 groups, while there was evidence that digging behavior may be affected by the different rearing experience. The inclusion of a 'standard strain or stock' in phenotyping protocols involving multiple inbred strains or lines of rats, mice and flies has obvious advantages by providing a reference point for inter-laboratory comparisons. The properties of inbred strains and outbred stocks favorable to their use as standards are discussed.

Variation in intake of sweet and bitter solutions by inbred strains of laboratory mice has helped identify genes related to taste behaviors; but similar information is not available for golden hamsters (Mesocricetus auratus ), a species used much in taste research. Thus, 6-hour, 1-bottle intake by water-replete hamsters of 7 inbred strains was measured for water and 2 concentrations of sucrose, maltose, D-phenylalanine (D-Phe), and sodium saccharin, which are sweet; and quinine.HCl, L-phenylalanine (L-Phe), caffeine, and sucrose octaacetate (SOA), which are bitter to humans. Difference scores (DIF), calculated as solution intake minus mean baseline water intake (mL) for each animal, were evaluated by analysis of variance. Compared to ACN, CN, APA, APG, and CBN, five strains with similar DIF for all compounds, GN, an ancestral strain of ACNT, and ACNT preferred sucrose, caffeine, and SOA more strongly; ACNT also preferred saccharin and maltose more strongly and rejected quinine more strongly. Narrow sense heritabilities for the 6 compounds for which strain differences were revealed ranged from 0.31 to 0.57. Genetic correlations indicated the strain variations in intake of sucrose, saccharin, SOA, and caffeine were coupled; a statistical association with several possible interpretations. Intakes of the two amino acids, preferred D-Phe and aversive L-Phe, did not reveal strain differences, and heritability ranged from 0.13 to 0.23 for the two optical isomers. Thus, although, compared to mice, genetic variation in laboratory hamsters may be small, genetic differences that influence taste behaviors in existing strains may help identify relevant genes.

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Abstract:The present study was undertaken to investigate the relationship between the emotionality and the modulation of ultrasonic vocalizations in Tsukuba High Emotional (THE) and Tsukuba Low Emotional (TLE) strain rat pups 3-18 days old. The THE pups, while isolated from their dam and littermates and placed in a cold environment, emitted ultrasonic isolation calls at a high rate until day 15. In contrast, ultrasound production was at a consistently low level throughout the test period in the TLE pups. The ultrasonic isolation calls of THE pups were attenuated to the same level as those of the TLE pups after administration of diazepam (1 mg/kg, sc), a benzodiazepine receptor agonist, at 6 and 12 days of age. These findings suggest that the high emotionality of the rat pups was reflected largely by the emission of ultrasounds in response to isolation distress rather than the number of the benzodiazepine receptors in the brain that might play a role in physiologic mediation of the rat pup isolation call. Key words: diazepam, emotionality, Tsukuba emotional strain rat pups, Ultrasonic vocalizations with 30-50 kHz sound frequencies, and the ultrasound emissions are intensified when a pup is isolated and placed in a cold environment [1,15]. The ultrasonic isolation calls of rat pups stimulate maternal retrieving behaviour [3,18,19].There are, however, some pups in a litter, and sometimes whole litters, that emit no, or only very few, ultrasonic vocalizations, even if they are isolated from their dam and littermates and placed in a cold environment. Thus, the motivation for the emission of ultrasounds in infant rats is not entirely clear.