Mice selectively bred for open-field thigmotaxis: life span and stability of the selection trait

In 2 experiments, the authors examined 69 mice selectively bred for high or low levels of open-field (OF) thigmotactic behavior (high open-field thigmotaxis [HOFT] and low open-field thigmotaxis [LOFT], respectively). They found that the strains differed in defecation during the 60-min exposure to the OF. Furthermore, the strains differed with regard to their life spans: The more thigmotactic HOFT mice lived longer than the LOFT mice. The strains were not differentiated by food intake or excretion. The strain difference in thigmotaxis was not age dependent, and it persisted in the home-cage condition as well. Neither the location (center or wall) of the starting point nor the shape (circular or square) of the OF arena affected the difference in wall-seeking behavior between the two strains. The authors concluded that the difference in thigmotaxis (or emotionality) between the HOFT and LOFT mice is a stable and robust feature of these animals.     

Prepartum and postpartum open-field behavior and maternal responsiveness in mice bidirectionally selected for open-field thigmotaxis

The authors examined pre- and postpartum open-field (OF) behavior and maternal responsiveness in mice that they bidirectionally selected for OF thigmotaxis. The authors tested 40 female mice under 3 conditions: prepartum OF, postpartum OF, and a pup retrieval test. In both OF conditions, the high OF thigmotaxis (HOFT) mice were more thigmotactic but explored and reared less than the low OF thigmotaxis (LOFT) mice, indicating that the HOFT mice were more emotional. In the postpartum condition, the HOFT mothers also defecated more and ambulated less than the LOFT mothers. The increase in grooming after parturition was more conspicuous among the LOFT mothers than among the HOFT mothers. The LOFT mothers were also more attracted to their pups in the OF, but the retrieval test did not show any substantial line differences. The results suggested that the line difference in emotionality was more pronounced during lactation than during pregnancy, although parturition exerted no effect on thigmotaxis.     

Open-field thigmotaxis during various phases of the reproductive cycle

Three experiments were conducted on female Swiss albino mice in order to determine whether open-field (OF) ambulation and thigmotaxis (wall-seeking) alter both as functions of reproductive phases such as estrus, mating, gestation, partus, lactation, weaning, as well as of presence, absence and OF location of a newborn pup. The results revealed increased thigmotaxis as an effect of estrus ( p < 0.001). From mating to one month postpartum a growing tendency towards maternal occupation of centre OF partitions was observed. Maternal ambulation reached its peak two days before partus but dropped to its lowest level during the lactation period at which time the mice were the least wall-seeking. Ambulation was enhanced ( p < 0.001) in the presence of a pup regardless of Oft starting point and the pup's placement. However, when the mouse dam was initially placed together with the pup by the OF wall, she hardly penetrated centre units at all.     

A qualitative aspect of learning-sensitive open field ambulation in mice

Maze training was shown to affect qualitative aspects of the learning-sensitive open-field (OF) ambulation in male Swiss albino mice. The changes in thigmotactic (wall-seeking) behaviour were most pronounced when significant signs of learning occurred, usually on the third day of training. Also daily changes in thigmotaxis from before to after training were found. Mice not subjected to maze training exhibited a different thigmotactic pattern of behaviour. The present series of experiments indicated that separate starting-points (centre or wall) influenced the thigmotactic behaviour as opposed to the shape of the OF (circular or square).     

Open-field nidus and pullusindices in Mus Musculus L.

Swiss albino mice ( Mus Musculus L. ) were studied in an open field (OF). The question whether laboratory rodents were more attracted to a nest equipped with familiar odoriferous cues from the home-cage bedding or to signals of an unfamiliar newborn pup inserted in the OF was addressed. The results of the three quantitatively recorded OF behaviors, ambulation, retrieval and radial latency , indicated that in females both ambulation and retrieval were enhanced by the presence of a pup in a nestless field; in males locomotion was suppressed by a nest in a pupless OF. In the case of both sexes radial latency was determined by the OF position of a nest. A comparison between the two qualitative assessments, the nidus and pullus indices, yielded that the sex of the adult and the OF positions of both targets equally impacted attraction towards both nest and pup.     

Maze-running and thigmotaxis in mice: Applicability of models across the sexes

Both male (n = 244) and female (n = 223) Swiss albino mice displayed a U-shaped pattern of thigmotaxis (wall-seeking) in a circular open-field (OF) before and after a daily maze-running. A significant increase of mice's tendency to occupy the inner partitions of the OF after the maze trial on the last three out of five days of training was observed. When factor analyzed, the variables indicating the wall-seeking behaviour of both sexes were divided into two factors interpreted as "spontaneous" in conjunction with the first three to four maze trials and as "learning-related thigmotactic behaviour" during the subsequent trials in the course of the learning process.     

父母教养行为、自主与大学生职业生涯探索的关系

该研究以676名大学生为被试,采用问卷法考察了大学生的父母教养行为、自主与职业生涯探索的关系。结果表明：（1）父母教养行为显著预测大学生的职业生涯探索。其中,父亲和母亲情感温暖和理解、母亲监控与保护、父亲监控维度为正向预测,而父亲和母亲惩罚严厉维度是负向预测;（2）自主对大学生的职业生涯探索有明显的预测作用。投射调控、认同调控和整合调控在其中起着主要的作用,且认同调控的解释率最高;（3）父母教养行为通过自主间接影响大学生的职业生涯探索,其中,自主在父母情感温暖与理解、母亲监控与保护与大学生职业生涯探索的关系间起完全中介作用。     

Phosphorylation state of CREB in the rat hippocampus: a molecular switch between spatial novelty and spatial familiarity?

The activation of cAMP response element-binding protein (CREB) after a learning experience is a common feature in the formation of several associative memories. We recently demonstrated that the increase in the hippocampal phosphorylated CREB (pCREB) levels 1 h after a short exploration of an open field (OF) was associated to detection of spatial novelty and was not related to the memory formation of habituation in this non-associative learning paradigm. Moreover, after a long training of three OF sessions, hippocampal pCREB levels were below to that observed in control rats. The present results show that such decrease does not correlate with memory retrieval or improvement in long-term memory of habituation. Instead, it is associated with the familiarity to the arena. Our experiments revealed that the relevant variable to induce CREB deactivation was the prolonged exploration of the arena (30 min). A 15 min OF exploration was ineffective. Furthermore, the last 5 min period of a prolonged exploration was crucial to change CREB phosphorylation state: when exploration took place in a novel arena the level of pCREB increased; in contrast, when it was performed in the familiar OF, pCREB levels decreased. Taken as a whole, our results suggest that CREB phosphorylation state in the hippocampus switches in response to exposure to a novel or to a familiar spatial environment.     

Some fear-potentiating effects of fluprazine hydrochloride in mice

The fear-potentiating effects of fluprazine hydrochloride were explored in a series of five experiments. The drug was found to strongly inhibit entry into a novel open field, exploration of a complex maze, or approach to a novel object placed in the animal's home cage. Time sampling techniques were used to assess drug effects on frequencies of immobility, activity, and grooming and rearing responses prior to and for 70 min after footshock. There were no group differences during the 10 min immediately following shock but the groups diverged steadily in immobility, activity, and grooming for the remainder of the observations. Post-shock activity and grooming responses increased steadily towards baseline values among control mice but remained at low levels or declined among drug-treated mice. Immobility responses declined steadily among control mice but increased substantially among the fluprazine-treated mice throughout post-shock observations. Pairs of male mice treated with fluprazine were also found to maintain greater intermouse distances in a novel linear runway than pairs of undrugged adult males, juvenile males, or male-female pairs. It is suggested that fluprazine hydrochloride both potentiates fear and alters its time course in addition to interfering in some way with normal olfactory processes.     

Sex-dependent habituation to novelty in rats

Male and female rats were familiarized with one-half of an exploration box for 30 or 60 minutes. When later tested, females showed higher preferences for the other novel half than males. Females also showed higher levels of rearing and ambulation. No sex differences were evident for grooming, freezing or defecation. The results were interpreted as females having habituated to the forced-exposure novelty of the familiar half of the apparatus more rapidly than males when the familiarization period was relatively short. With a longer period, males would have had more time to reach a similar level of habituation to that attained by females familiarized for 30 minutes. Relationships between novelty preferences and both rearing and ambulation as indices of exploration were also discussed in the light of significant correlations for males only.     

Neophobia in spontaneous hypertensive (SHR) and normotensive control (WKY) rats

Latency of approaching a novel object (white-colored cube) placed in an unfamiliar open field, duration of object exploration, ambulation, rearing, grooming, and defecation were investigated in spontaneous hypertensive rats (SHR), their genetic normotensive controls (WKY), and standard Laboratory rats of Wistar origin (Tif:RAIf). The parameters measured were taken as indices of fear due to novelty (neophobia). Remarkable differences in behavior of all three strains were observed. By comparison to RAIf and WKY rats, SHR showed decreased neophobia as reflected in the significantly shorter latency of approaching the object and enhanced ambulation and rearing activity in the open field. By comparison to RAIf rats SHR also showed reduced grooming and defecation. WKY rats distinguished themselves from both SHR and RAIf by almost total absence of all responses in this test situation. This behavioral suppression was antagonized by 7.5 mg/kg ip of chlordiazepoxide. The results of this study further support the notion that, by comparison to standard laboratory rats, both SHR and WKY rats show possible genetically determined, altered behaviors which are diametrically opposite to each other.     

家庭社会经济地位、父母教养行为与大学生职业生涯探索的关系

该研究以676名大学生为被试,采用问卷法考察了家庭社会经济地位、父母教养行为与大学生职业生涯探索的关系。结果表明:(1)家庭社会经济地位与自我探索、环境探索、自我-环境匹配度探索、探索意向间显著正相关;(2)父母教养行为显著预测大学生的职业生涯探索。其中,父亲和母亲情感温暖和理解、母亲监控与保护、父亲监控维度为正向预测,而父亲惩罚严厉维度是负向预测;(3)家庭社会经济地位不仅对大学生的职业生涯探索有独立的预测作用,还通过母亲情感温暖和理解、母亲监控与保护的中介作用正向预测这一变量。     

Sex-dependent habituation to novelty in rats

Male and female rats were familiarized with one-half of an exploration box for 30 or 60 minutes. When later tested, females showed higher preferences for the other novel half than males. Females also showed higher levels of rearing and ambulation. No sex differences were evident for grooming, freezing or defecation. The results were interpreted as females having habituated to the forced-exposure novelty of the familiar half of the apparatus more rapidly than males when the familiarization period was relatively short. With a longer period, males would have had more time to reach a similar level of habituation to that attained by females familiarized for 30 minutes. Relationships between novelty preferences and both rearing and ambulation as indices of exploration were also discussed in the light of significant correlations for males only.     

Effects of social stress on tumor development in dominant male mice with diverse behavioral activity profiles

We examined the influence of individual psychological profile and social behavior on tumor development in dominant male mice. Male OF1 mice were subjected to an open field test (OFT) to observe their motor activity and latency. Subsequently, the animals were divided into three groups: Stress-Non-Inoculated (SNI), Stress-Inoculated (SI) and Control-Inoculated (CI). The SI and CI groups were inoculated with tumor cells and the SNI group with vehicle. SNI and SI were exposed to social stress with an anosmic intruder six (T1) and twenty one (T2) days after inoculation and their behavior was analyzed. After T2, subjects were put down and the pulmonary metastatic foci counted. SI developed greater pulmonary metastasis than CI, indicating an effect of stress despite the animal's dominant status. Active animals developed less pulmonary metastasis than their passive counterparts. No differences were found in social behavior at T1. Differences were found, however, in some behavioral categories at T2 between SI and SNI, and between active and passive animals. These differences indicate an effect of tumor development on social behavior that is more evident in passive subjects.     

Activity measures in stress-attenuated novelty tests as possible analogues for extraversion in rats: Some experimental results

In an attempt to extend and validate Garcia-Sevilla's (1974) hypothesis proposing ambulation in a non-stressful open field (OF) as an animal analogue of human extraversion, ambulatory behaviour and rearing behaviour were studied and compared in several experiments with genetically-unselected rats. The effects of variation of OF auditory stimulation level, the correlation with a two-way avoidance-learning situation and the effects of a stimulant dose of d-amphetamine and an anxiolytic one of diazepam upon rearing and ambulatory behaviours were studied. All in all, our results support some of the requirements of the hypothesis, but also generate some additional problems. The results show that the number of rearings could be a better and more sensitive measure of variations in the level of arousal and a better predictor of shuttle-avoidance conditioning than ambulation. However, all activity measures are at least moderately intercorrelated, and they become grouped when results are factor analysed. All the results are discussed with reference to Eysenck's personality theory and Gray's anxiety theory, and it is concluded that these measures are too multidetermined and too poorly controlled to represent correctly and in a direct form a personality dimension such as Extraversion. Anyway, this attempt could be a good point of departure for discovering more efficient animal behavioural measures of arousability.     

Behavioral changes over several successful agonistic encounters between male mice: Effects of type of “standard opponent”

This study assessed whether two types of non-aggressive “standard opponents” (“intact” and “anosmic” group-housed males) produced similar behavioral changes in isolated OF1 male mice given several experiences of victory. Experimental groups confronted either intact or anosmic opponents every two days until they had completed four encounters. The behavioral changes were recorded using a detailed ethologically inspired analysis. These changes were clearly different depending on the opponent type. When intact opponents were used, experimental subjects increased the time spent in digging, non-social exploration, explore from a distance, and attack over encounters, but showed decreased time spent in threat and a decreased latency to the first attack. In encounters with anosmic opponents, only declines in the latencies to threat and attack were noted. Moreover, the experimental groups differed in their behaviors over encounters. Those confronting intact opponents spent less time in social investigation, more time in explore from a distance and threat, and showed a shorter latencies to threat and attack than counterparts confronting anosmics. These results suggest that, although both types of “standard opponents” are similar in their non-aggressiveness, they elicit rather different behavioral responses in their adversaries. These findings provide additional support for the view that the type of opponent used in studies on intermale aggression is of paramount importance. Indeed, the use of different types of “standardized non-aggressive opponents” appears to be an important source of variability between studies. © 1994 Wiley-Liss, Inc.     

Species-typical taxic behavior and event-reinforcer interactions in conditioning

The role of species-typical taxic behavior in conditioning was studied using thigmotaxis (wall hugging) in rats. Running toward or staying near walls in an open-field apparatus was assumed to be compatible with the rat's defensive behavior, and running to or staying in open spaces was assumed to be incompatible. With large food rewards no differences between the center and side responses were found in acquisition under continuous or intermittent reward, but the center response showed greater suppression after contingent punishment was applied on nonreward trials. Two additional experiments showed that differences between center and side responses occur during extinction when avoidance of shock but not when food is the reinforcer. The results suggest that instances of response-reinforcer interactions may be predicted by knowledge of species-typical defensive behavior and that reactions elicited by shock are not always identical to those elicited by frustration in their consequences for the performance of conditioned behavior.     

Brain weights correlate with behavioral parameters in individual inbred mice housed in a common and enriched environment

Fifty 8-week-old Balb/c mice were individually identified and housed together in a large and enriched environment for 5 months. Maze and open field exploration, response to an aversive noise, swimming, and induced grooming tests were applied to each mouse in an initial search for possible relationships between brain morphology and spontaneous behavior in isogenic individuals living in a complex social and physical environment. The tasks generated 39 quantitative behavioral indices which include locomotion, rearing, still, and grooming bout frequencies, latencies, total, and mean bout durations. At the end of the tests, the 7-month-old mice were sacrificed and the fresh weights of their whole brain, cerebellum, brain stem, diencephalon, telencephalon, and prosencephalon were rapidly obtained. Behavioral data have wide variations and do not adjust to normal population distributions. Means of the same parameter differ between tests. A Spearman correlation matrix of all data yielded many significant correlations between indices of the same task which can be interpreted in terms of time budget and sequence probability. Significant correlations between indices of different tests suggest diverse emotionalities, exploratory strategies, and motor skills. The correlations between body and brain weights and among separate brain regions were not significant. There were several low but significant correlations between brain weights and behavioral indices. Such correlations, the resulting factors, and significant behavioral differences between mice with large and small brains suggest that mice displaying low motor activity in novel environments have larger brains and forebrain/hindbrain ratios than mice with high activity, and that animals with high scores of some specific behaviors have larger brain areas physiologically related to such behaviors.(ABSTRACT TRUNCATED AT 250 WORDS)     

A developmental-genetic analysis of aggressive behavior in mice: IV. Genotype-environment interaction

To assess the extent of plasticity in behavioral development after directional selection for aggressive behavior, male mice were reared and tested in selected social rearing and testing conditions. After four generations of selective breeding, the lines differed in all attack measures when tested in a dyadic assessment following isolation rearing. Line-specific effects of isolation vs. group rearing were demonstrated, and longitudinal studies showed the ontogenetic pattern of difference between lines to be substantially changed by conditions of rearing and testing. The social-interactional processes that might produce the developmental genotype-environment interaction were investigated. Line-specific interaction patterns within long-established sibling groups predicted aggressive behavior in cross-situational dyadic assessments. Group rearing attenuated most line differences in aggressive measures, but the high-aggressive line was more likely than the low-aggressive line to persist in attacking over consecutive days of observation. Cross-fostering in early development did not significantly change adult aggressive behavior. Some implications of a developmental-genetic approach to the study of social interactions are discussed.     

Anxiogenic-like effects of gamma-hydroxybutyric acid (GHB) in mice tested in the light-dark box

Gamma-hydroxybutyric acid (GHB) is a drug with abuse potential, popularly known as "liquid ecstasy". It is an endogenous compound of the mammalian brain which satisfies many of the criteria for consideration as a neurotransmitter or neuromodulator. In this study, the effects of acute administration of GHB (40, 80 and 120 mg/kg, ip) on anxiety, tested in the light/dark box, were examined in male mice of the OF.1 strain. Likewise, we compared the behavioural profile of GHB with that induced by mCPP (1 mg/kg, ip), a compound with known anxiogenic actions. GHB-treated mice spent notably less time in the lit area (40 and 80 mg/kg) and more time in the dark area (all doses), whereas the total number of 'rearings', transitions and latency were significantly reduced. A very similar behavioural profile was observed in mCPP-treated animals. Overall, these findings indicate that GHB exhibits anxiogenic-like properties in male mice. It is suggested that the anxiogenic effects of GHB could be related to its ability to modulate GABA and/or dopaminergic receptors.