Inhomogeneous hippocampal activation along the rostrocaudal axis in mice after exploration of novel environment

Levels of the c-Fos protein expression in neurons were used as an index of neural activation in the hippocampus of C57BL/6 mice after their exploration of novel environments. C-Fos expression was measured at 8 levels along the rostrocaudal axis of the hippocampus. In Experiment 1, C57BL/6 mice were trained in a modified 8-arm radial maze to find the entry to a home cage through a target arm (1 day, 6 trials). Animals of control group were trained to enter the home cage through an isolated arm. In mice trained in 8-arm maze, functional rostrocaudal inhomogeneity of hippocampus was found. C-Fos expression was increased, mainly, in the caudal parts of CA1, CA3 and dentate gyrus as compared to the control group. In Experiment 2, C57BL/6 mice were tested (1 day, 6 trials) in a novel open-field arena. In this case, c-Fos activity was increased in CA1 (to a greater extent in the caudal than in rostral parts) and CA3 and dentate gyrus (equally in rostrocaudal direction). Significant positive correlations between the exploration activity and density of c-Fos positive cells were found in both experiments. The findings suggest that exploration in novel environment differentially affects the hippocampal subfields along the hippocampal rostrocaudal axis.     

Genetic trade-off between abilities to avoid attack and to mate: a cost of tonic immobility

Consistent individual differences in correlated behaviours across contexts or situations, that is, behavioural syndromes, have recently been identified as an important factor shaping the evolution of behavioural traits, because of their potential for explaining trade-offs in behavioural responses. We examined a genetic link between abilities to mate and to avoid predation from the viewpoint of two genetically correlated behavioural traits; tonic immobility (TI), which is considered to be an antipredator behaviour, and activity levels in the red flour beetle, Tribolium castaneum. Males derived from two strains artificially selected for divergent durations of TI were used in the present study: the L strain (with longer duration and higher frequency of TI) and the S strain (shorter duration and lower frequency of TI). We found that males of the L strain had higher survival rates in predatory environments than those of the S strain, and lower mating success even in predator-free environments. To our knowledge, this is the first empirical study showing a genetic trade-off between abilities to mate and to avoid predation in relation to behavioural syndromes, using individuals exhibiting different behavioural strategies.     

Absence of anxiolytic response to chlordiazepoxide in two common background strains exposed to the elevated plus-maze: importance and implications of behavioural baseline

Although genetic background is acknowledged as a potentially important determinant of mutant phenotypes, publications on genetically modified mice far outnumber those on progenitor strains. We have recently reported major differences in basal anxiety levels (elevated plus-maze & light/dark exploration) among three strains (C57BL/6JOlaHsd, 129/SvEv and 129S2/SvHsd) employed as progenitor stock in European laboratories (Rodgers et al. in press). Furthermore, the phenotypes of these inbred strains differed significantly from that of an outbred strain (Swiss-Webster) commonly used in behavioural pharmacology. In view of these findings, the present study assessed possible differences in the anxiolytic efficacy of chlordiazepoxide (0, 7.5 & 15.0 mg/kg, IP) in three of these strains (Swiss-Webster (SW), C57BL/6JOIaHsd (C57) & 129S2/SvHsd (129)). Experimentally naive mice were exposed to the elevated plus-maze, sessions were videotaped and behaviour analysed using ethological software. The performance of control subjects confirmed significant strain differences in basal levels of activity (SW > C57 > 129) and anxiety-related behaviours (129 = SW > C57), with hypolocomotion dominating the 129 profile. SW mice displayed an anxioselective response to both doses of chlordiazepoxide (CDP), with significant reductions in open arm avoidance and risk assessment observed in the absence of any change in general activity. In direct contrast, the lower dose of CDP (7.5 mg/kg) was without effect in either inbred strain, whereas treatment with 15.0 mg/kg induced a profile indicative of muscle relaxation/mild sedation in C57 mice and virtually abolished all behavioural activity in 129 mice. Although the absence of an anxiolytic response to CDP in C57 mice may be attributed to their low basal anxiety levels, the profile of 129 mice strongly suggests an abnormality in benzodiazepine/GABAA receptor function. The implications of these findings for research on mutant mice are discussed.     

Changes in several functions of murine peritoneal macrophages by N-acetylcysteine and thioproline ingestion. Comparative effect between two strains of mice

The administration of the thiol compounds, N-acetylcysteine (NAC) and in particular thioproline (thiazolidine-4-carboxylic acid) at 0.1% w/w concentration in the diet, improves lymphocyte functions in old female Swiss mice, as has been shown in our previous studies. In the present work, adult mice from two different strains, namely BALB/c (an inbred strain) and OF1-Swiss (noninbred strain), were fed a diet supplemented with the above dose of each thiol compound jointly for five weeks. At 28 weeks of age, peritoneal cell suspensions were obtained and different steps of the phagocytic process, the most representative activity of macrophages, as well as interleukin-1beta (IL-1beta) production, were studied. Thus, adherence to substrate, mobility directed to a chemoattractant gradient (chemotaxis), ingestion of inert particles and superoxide anion production were analysed. The results show that diet supplementation with NAC plus thioproline increased all macrophage functions studied with the exception of superoxide anion production, which was decreased. These effects were more evident in macrophages from Swiss mice, whereas in BALB/c mice the stimulation of phagocytosis and IL-1beta production was lower and no differences were seen after treatment in adherence and superoxide anion production. These data suggest that immune function can be improved in adult mice by administration of the above thiol compounds, especially in the noninbred strain of OF1-Swiss mice.     

Temporal differentiation in two strains of small rodents: a wood mouse (Apodemus sylvaticus) and an albino mouse (Mus musculus OF1)

Wood mice (Apodemus sylvaticus) and OF1 albino mice (Mus musculus) were compared over durations ranging from 0.5 to 7 s, using the differential reinforcement of response duration schedule (DRRD) and a 'platform' response, i.e. staying on a small platform for a specified criterion duration to be reinforced. Species-related differences were found for mean response durations, efficiency and the number of trials needed to reach a preset performance criterion. Coefficients of variation of response durations did not differ. Overall, OF1 mice needed more trials than wood mice to reach a temporal criterion. However, over 3-7 s, data from both strains almost fitted the behavioral assumptions of Scalar Timing theory. Performance of mongolian gerbils (Meriones unguiculatus) trained in a similar setting was shown for visual comparison.     

Twenty-three generations of mice bidirectionally selected for open-field thigmotaxis: selection response and repeated exposure to the open field

We examined: (a) the response to bidirectional selection for open-field (OF) thigmotaxis in mice for 23 generations and (b) the effects of repeated exposure (during 5 days) on different OF behaviors in the selectively bred high OF thigmotaxis (HOFT) and low OF thigmotaxis (LOFT) mice. A total of 2049 mice were used in the study. Prior to the testing in the selection experiment, the mice were exposed to the OF apparatus for approximately 2 min on each of 4 consecutive days. Thus, the selection was based on the scores registered on the 5th day after the four habituation periods. The HOFT mice were more thigmotactic than the LOFT mice in almost each generation. The HOFT mice also tended to rear less than the LOFT mice, which was explained by the inverse relationship between emotionality and exploratory tendencies. The lines did not generally differ in ambulation. Sex differences were found in thigmotaxis, ambulation, and rearing. In the repeated exposure experiment, the development of nine different OF behaviors across the 5 days of testing was addressed. Both lines ambulated, explored, and reared most on the 1st, 4th, and 5th days. Grooming and radial latency decreased and thigmotaxis increased linearly across the testing days. Line differences were found in ambulation, exploration, grooming, and rearing, while sex differences were manifested in ambulation and exploration. The line difference in thigmotaxis was evident only on the 5th day. Temporal changes were partially at variance with the general assumptions. OF thigmotaxis was found to be a powerful characteristic for producing two diverging lines of mice.     

QTL analysis of measures of mouse home-cage activity using B6/MSM consomic strains

The activity of mice in their home cage is influenced greatly by the cycle of light and dark. In addition, home-cage activity shows remarkable time-dependent changes that result in a prominent temporal pattern. The wild-derived mouse strain MSM/Ms (MSM) exhibits higher total activity in the home cage than does C57BL/6 (B6), a commonly used laboratory strain. In addition, there is a clear strain difference in the temporal pattern of home-cage activity. This study aimed to clarify the genetic basis of strain differences in the temporal pattern of home-cage activity between MSM and B6. Through the comparison of temporal patterns of home-cage activity between B6 and MSM, the pattern can be classified into five temporal components: (1) resting phase, (2) anticipation phase, (3) 1st phase, (4) 2nd phase, and (5) 3rd phase. To identify quantitative trait loci (QTLs) involved in these temporal components, we used consomic strains established from crosses between B6 and MSM. Five consomic strains, for Chrs 2T (telomere), 3, 4, 13, and 14, showed significantly higher total activity than B6. In contrast, the consomic strains of Chrs 6C (centromere), 7T, 9, 11, and 15 were less active than B6. This indicates that multigenic factors regulate the total activity. Further analysis showed an impact of QTLs on the temporal components of home-cage activity. The present data showed that each temporal component was regulated by different combinations of multigenic factors, with some overlap. These temporal component-related QTLs are important to understand fully the genetic mechanisms that underlie home-cage activity.     

A simple and reliable test of olfactory learning and memory in mice

The present paper describes a quick and efficient method for assessing olfactory discrimination learning in mice. In training mice received trials in which one odor (CS+) was paired with sugar and another odor (CS-) was paired with no sugar. When the mice were subsequently placed in a chamber with CS+ odor at one end and CS- odor at the other, they spent more time digging in CS+ than in CS- odor. In Experiment 2 mice trained with this procedure and tested after 60 days also spent more time digging in CS+ than CS- in the test phase, indicating that this olfactory discrimination task is effective for assessing long-term memory. In addition to the outbred strain of CD1 mice used in Experiments 1 and 2, C57Bl/6NCr/BR and DBA/2NCr/BR mice used in Experiment 3 also acquired this learned odor discrimination. Moreover, Experiment 4 showed that DBA animals were capable of acquiring this odor discrimination after receiving only two training trials (one exposure each to CS+ and CS-) per day for 4 days.     

Cereal aversion in behaviourally resistant house mice in Birmingham, UK

In 1986, house mice in a small defined area of inner Birmingham were reported as not taking a variety of rodenticides from bait containers, a phenomenon labelled 'behavioural resistance'. This study investigated behavioural resistance by comparing the food preferences of West Midlands behaviourally resistant (WMBR) mice with those of normal (BC) mice. Nine bait boxes each containing one of nine different foods (cheese, chicken, tuna fish, peanut butter, canary seed, Cat stars, wheat, PCD (MOD) pellets and Non-tox) were introduced to 12 WMBR and seven BC sites (Experiment 1). The experiment was repeated in the laboratory with six pens of WMBR and six of BC mice (Experiment 2), and to investigate whether the preferences had a genetic basis the offspring were similarly assayed (Experiment 3). In each experiment the consumption of each food was measured over 7 days and the droppings around the bait boxes were counted to assess mouse activity. Food neophobia was noted in some populations of BC mice. Tested in the wild and in the laboratory WMBR mice showed an aversion to foods containing cereals, as did their offspring. These results, with other lines of evidence, strongly suggest that cereal aversion in WMBR mice has a physiological/genetic basis. Since cereal aversion allows WMBR mice to survive cereal-based rodenticidal baits, we conclude that WMBR mice have genetically based behaviours that allow them to survive poisoning regimes that kill other strains.     

Foraging behavioural changes induced by conspecific and heterosubspecific odours in two strains of wild mice

Mice in wild populations of the two subspecies Mus musculus domesticus and Mus musculus musculus may potentially compete for food. Because of the importance of olfaction in mice, we hypothesised that the presence of unfamiliar conspecific or heterosubspecific chemical cues could play a role in access to and use of food resources. We used an experimental design that tested this assumption with males from two strains, originated from wild populations of these subspecies, as subjects. Exploratory activity, latency of food approach, time and frequency on the food area, number of seeds eaten and foraging rate (number of seeds eaten/time on the food areax100) were compared for three different categories of odours (own, same strain and other strain odours) in both strains. In a foraging context, unfamiliar odours induced behavioural changes in male mice, especially an increase in exploratory activity from the more (same strain) to the less similar odour (different strain), and a reduction of time spent in the food area. Odour similarity related to genetic proximity in Mus and the cost-benefit ratio of an encounter are two possible explanations for the different processes involved in the treatment of odours in these two strains of mice.     

Frequency of interspecific mating in salamanders of the plethodontid genus Desmognathus: different experimental designs may yield different results

Heterosexual courtship trials were staged between dusky salamanders of two species ( Desmognathus fuscus and D. santeetlah ) from two allopatric populations in the southern Appalachian Mountains of eastern North America. Two experiments were conducted in order to test for effects of experimental design on estimates of the strength of sexual isolation between these species. In Experiment 1, frequencies of interspecific mating were determined when: (1) a male was presented with a conspecific and a heterotypic female successively; and (2) both types of females were presented simultaneously to a male. The frequency of interspecific mating by male D. fuscus was greatest when females were presented successively. The frequency of interspecific mating by male D. santeetlah was not influenced by method of female presentation. An index of sexual isolation of +0.29 was obtained between D. fuscus and D. santeetlah when females were presented successively, and of +0.63 when females were presented simultaneously. In Experiment 2, interspecific mating frequencies were determined in courtship arenas of two different sizes. No significant effect of arena size on frequency of interspecific mating was found for D. fuscus. In D. santeetlah , a trend towards greater mating frequency in small arenas was almost significant. These results suggest that interspecific mating frequencies (and thus estimates of the strength of sexual isolation between populations or species) may be sensitive to the experimental design employed. The validity and generality of this conclusion for other animals is an urgent, empirical issue.     

Cognitive assessment of mice strains heterozygous for cell-adhesion genes reveals strain-specific alterations in timing

We used a fully automated system for the behavioural measurement of physiologically meaningful properties of basic mechanisms of cognition to test two strains of heterozygous mutant mice, Bfc (batface) and L1, and their wild-type littermate controls. Both of the target genes are involved in the establishment and maintenance of synapses. We find that the Bfc heterozygotes show reduced precision in their representation of interval duration, whereas the L1 heterozygotes show increased precision. These effects are functionally specific, because many other measures made on the same mice are unaffected, namely: the accuracy of matching temporal investment ratios to income ratios in a matching protocol, the rate of instrumental and classical conditioning, the latency to initiate a cued instrumental response, the trials on task and the impulsivity in a switch paradigm, the accuracy with which mice adjust timed switches to changes in the temporal constraints, the days to acquisition, and mean onset time and onset variability in the circadian anticipation of food availability.     

Liquid culture carbon, nitrogen and inorganic phosphate source regulate nematicidal activity by fluorescent pseudomonads in vitro

AIMS: The aim of the present investigation was to determine the influence of nutrients on the nematicidal activity by Pseudomonas aeruginosa strain IE-6S+ and Ps. fluorescens strain CHA0 in vitro. METHODS AND RESULTS: Culture filtrate of IE-6S+ and CHA0 obtained from chemically defined medium caused mortality of Meloidogyne javanica juveniles in vitro and that growth medium amended with various C, N or inorganic phosphate (Pi) sources markedly influenced nematicidal activity of the two bacteria. Glycerol (C source), propionate (fatty acid precursor) and L-lysine (N source) enhanced nematicidal activity while glucose (C), L-valine (N) and Pi substantially repressed nematicidal activity of the two bacteria. CONCLUSION: Liquid culture amendments with various C, N or Pi sources modulate the biosynthesis of nematicidal agents to a different extent in vitro. SIGNIFICANCE AND IMPACT OF THE STUDY: Developing bacterial strains more responsive to certain environmental signals can be exploited for increased secondary metabolite production in pharmaceutical fermentations and offers new avenues to improve biocontrol.     

The use of image analysis to study the effects of residues of esfenvalerate on the locomotory behaviour of Panonychus ulmi and Typhlodromus pyri (Acari: Tetranychidae, Phytoseiidae)

The influences of esfenvalerate on mite behaviour were investigated by image analysis. Video recordings of the locomotory behaviour of two mite species were converted into a series of x,y coordinates that, when joined, closely resembled their paths. These coordinates were used to calculate walking speed, direction of travel, turning frequency, turn bias and tortuosity. Two experimental arenas were used: (1) a leaf disc arena for the European red mite, Panonychus ulmi and (2) a glass coverslip arena for Typhlodromus pyri. The behavioural responses of P. ulmi and T. pyri to esfenvalerate (field rate) indicated that these mites did not show a preference for the unsprayed halves of the arenas during the first 48 min. However, significant differences between most of the behavioural parameters to esfenvalerate residues were found with P. ulmi when whole arenas were compared. © Rapid Science Ltd. 1998     

The mapping of quantitative trait loci underlying strain differences in locomotor activity between 129S6 and C57BL/6J mice

Performance in the open field and rotarod paradigms, two common assessments of locomotor function, have been demonstrated to be strain dependent in mice. In this study, eight significant quantitative trait loci (QTL) for behavior phenotypes in either the open field or rotarod paradigms were identified between the 129S6 (129/SvEvTac) and C57BL/6J strains. These strains were chosen for comparison because of their frequent use in the generation of mutant mice from gene-targeted, embryonic stem cells. Two of the QTLs for horizontal distance traveled are located on Chromosomes (Chrs) 1 and 12 and closely replicate the findings of other groups using different strains of mice. Rotarod performance was influenced in an oppositional manner by two separate QTLs on Chr 1 and 2. Additionally, examination of several different aspects of behavior in the open field revealed significant QTLs for average speed (Chr 12), duration (Chrs 2, 16, and 18), time spent in motion (Chr 16), vertical movements (rearing) (Chrs 6 and 12), and vertical time (rearing time) (Chrs 6 and 12). Our finding of independent QTLs for these topographic components of open field activity supports the idea that they are separate and distinct from total horizontal distance traveled and should be studied independently. The QTLs described in this study, in combination with our panel of polymorphic chromosomal markers for 129S6 and C57BL/6J strains, will be useful in assessing the potential epistatic effects of parental strain background on the phenotypes of genetically modified mice.     

不同品系小鼠在三种常见抑郁检测方法中的行为学表现

目的探讨4种不同品系小鼠在3种实验（空场实验、悬尾实验及强迫游泳实验）中的行为学差异,为抗抑郁新药研究中的实验动物选择提供参考。方法利用空场实验检测C57BL/6、BALB/c、ICR、和昆明小鼠的自主活动能力和对新奇环境的探索能力;利用悬尾实验和强迫游泳实验检测它们在应激刺激下的行为绝望状态。结果在空场实验中,BALB/c、ICR和昆明小鼠的运动总路程、运动速度和运动时间明显高于C57BL/6小鼠（P〈0.05）,ICR和昆明小鼠的直立次数也明显高于C57BL/6小鼠（P〈0.05）;悬尾实验C57BL/6小鼠的不动时间显著长于其他3种品系小鼠（P〈0.05）,但是4种品系小鼠在强迫游泳实验中的不动时间差异无显著性。结论 C57BL/6小鼠自发活动量低,对新奇环境的探索能力差,并且在急性应激刺激下容易造成行为绝望,因此C57BL/6小鼠可能适合作为急性应激抑郁模型动物。     

Kinematic study of the temporal coupling between the components of transport and manipulation during reaching and grasping movements

In this study the temporal coupling between transport and manipulation components of prehension movements was tested. For this purpose two experiments were carried out. In Experiment 1 six normal subjects were required to reach and grasp one of three spheres located at three different distances (Blocked trials). In Experiment 2 a visual perturbation paradigm was used in which the location of the object to be reached and grasped could change at onset of arm movement (Perturbed trials). The results of this study exclude a temporal coupling between events of transport and manipulation components. On the contrary they suggest that manipulation component organizes its time course having information about the time required to reach the object.     

Oviposition of resistant and susceptible strains of Drosophila melanogaster in the presence of deltamethrin

Oviposition of three strains of Drosophila melanogaster in the presence of deltamethrin was observed. These strains had different levels of physiological susceptibility to deltamethrin. Two-choice tests were conducted with couples of flies in petri-dish arenas containing two oviposition dishes. On the first day of the experiment, females were given a choice between a treated oviposition dish and an untreated control dish. On the second day of the experiment, two control oviposition dishes were given to females. Although individual females showed a tendency to aggregate their eggs in one of the dishes, control experiments demonstrated an overall equal distribution of eggs between the dishes. When one of the two oviposition dishes in the arena was treated with deltamethrin, the percentage of females ovipositing and the mean number of eggs laid by females were reduced, compared with control arenas. Females avoided the treated oviposition dish and laid significantly more eggs on the control dish. Furthermore, when the deltamethrin concentration was increased on the first day, female flies postponed their oviposition and laid significantly more eggs on the second day. The resistant strain, SR, demonstrated the same capacity to select the untreated site for oviposition as the susceptible strain, but it showed a smaller oviposition reduction and egg retention. The relationship between physiological and behavioural susceptibility to deltamethrin is discussed.     

The role of hair in swimming of laboratory mice: implications for behavioural studies in animals with abnormal hair

Animal swimming tests, such as the forced swim test, are extensively used in biomedical research to study rodent behaviour. Hair and skin exposed to water may be an important factor affecting the performance in this test. Since various hair and skin abnormalities are not uncommon in genetically modified or drug-treated laboratory animals, this test may be inappropriate for these animals. Because on occasions it is necessary to screen their swimming behaviour, in the present study we aimed to assess the role of hair in swimming of laboratory rodents in the forced swim test, widely used in behavioural research. For this, we shaved laboratory mice (129S1 strain) and compared their swimming patterns with those of unshaven controls. Overall, shaving mice did not affect their swimming behaviours in the 5 min forced swim test. Our results indicate that hair condition is not an important factor in the forced swim test for this mouse strain, and suggest that this test may have wider utility for behavioural analyses of mice with abnormal hair.     

Individual differences in plasticity and sampling when playing behavioural games

When engaged in behavioural games, animals can adjust their use of alternative tactics until groups reach stable equilibria. Recent theory on behavioural plasticity in games predicts that individuals should differ in their plasticity or responsiveness and hence in their degree of behavioural adjustment. Moreover, individuals are predicted to be consistent in their plasticity within and across biological contexts. These predictions have yet to be tested empirically and so we examine the behavioural adjustment of individual nutmeg mannikins (Lonchura punctulata), gregarious ground-feeding passerines, when playing two different social foraging games: producer-scrounger (PS) and patch-choice (PC) games. We found: (i) significant individual differences in plasticity and sampling behaviour in each of the two games, (ii) individual differences in sampling behaviour were consistent over different test conditions within a game (PC) and over a six month period (PS), (iii) but neither individual plasticity nor sampling behaviour was correlated from one social foraging game to another. The rate at which birds sampled alternative tactics was positively associated with seed intake in PS trials but negatively associated in PC trials. These results suggest that games with frequency dependence of pay-offs can maintain differences in behavioural plasticity but that an important component of this plasticity is group- and/or context-specific.