Septal damage in infant and adult rats: Effects on activity,emotionality, and muricide

Septal lesions produced signs of increased emotionality in the adult rat, the septal syndrome (hyperresponsiveness to handling; in the open field: decreased rearing and ambulation activity, increased defecation, deficient habituation) being more or less complete and more or less marked depending on the age at which the lesion was performed (7 days or 3 months), the extent of the lesion (restricted to the septum or extending to more ventrally located structures) and the environmental conditions in which the animals were reared (in groups or in isolation). All septal lesions provoked a similar and significant increase in the probability of occurrence of mouse-killing behavior, irrespective of age of operation, extent of lesion and kind of rearing environment. In a 24-hour actography starting at 11:30 a.m., the rats septalectomized at adult age were less active than controls during the initial period, while all septals were markedly more active than controls during the night period. Early septal lesions only transiently disrupted weight gain. The results obtained point to complex interactions between the effects of early brain damage and environmental conditions.     

Correlative effects of psychogenetic selection: A study of the roman high and low avoidance strains of rats

A sample of 86 rats of the RHA and RLA strains, selectively bred in Rome for speed of acquisition of conditioned avoidance responses (CAR), was given the open-field test of emotionality, and re-tested for conditioning in their new environment. Both sexes were included in a balanced-order design. The standardized open-field test and a conventional shuttle-box with buzzer as the conditioned stimulus and shock as the unconditioned stimulus were used. The results show that the Roman strains do not differ in respect of open-field defecation. While the RHA strain was confirmed as superior in measures of CAR formation, it was also found to be significantly more active both in the open-field (ambulation) and in inter-trial activity during conditioning. No effects attributable either to order of test administration or the previous history of the subjects were detected, and those due to their sex merely confirmed previous findings. These results are contrasted with the findings for the Maudsley strains of reactive and non-reactive rats which differ significantly in respect of emotional elimination as a result of a similar selection procedure, but which also display a similar difference in CAR acquisition and in mature body weight.     

Crossfostering in mice selectively bred for high and low levels of open-field thigmotaxis

The main purpose of this research was to investigate whether the difference in open-field (OF) thigmotaxis between mice selectively bred for high and low levels of wall-seeking behavior originated from genetic or acquired sources. Unfostered, infostered, and crossfostered mice were compared in two experiments in which the effects of strain, sex, and fostering on ambulation, defecation, exploration, grooming, latency to move, radial latency, rearing, thigmotaxis, and urination were studied. These experiments revealed that OF thigmotaxis was unaffected by the foster condition and thus genetically determined. The selected strains of mice also diverged repeatedly with regard to exploration and rearing. The findings are in line with the previously described existence of an inverse relationship between emotionality and exploration.     

Multivariate analysis of putative measures of activity, exploration, emotionality, and spatial behavior in the hooded rat (Rattus norvegicus)

Hooded rats were tested in six situations representing the variables of activity, exploration, emotionality, and spatial preference, detection of change, and learning. The activity, exploration, and emotionality variables and spatial variables were analyzed in separate multivariate analyses, followed by an analysis of the entire set. The first of these resulted in four components: activity, exploration and emotionality, reactivity to handling, and autonomic reactivity (defecation). Four components, defined by the following variables, emerged from the spatial analysis: (a) the tendency to circle, circling direction, and spatial learning; (b) heading error in spatial learning and reversal and open-field directional preference; (c) spatial reversal and direction of turn to escape restraint; and (d) detection of change in spatial arrangement and directional preference in the detection task. The final analysis investigated relations between the activity, exploration, and emotionality variables and the spatial variables, finding only two. The clear dimensionality of these behavioral repertoires emphasizes how important it is to recognize the distinctions among them.     

Sex differences in ambulation and defecation in the degu (Octodon degus)

The degu, a hystricomorph rodent, was studied in both an open-field (OF) and running-wheel testing situation. Of primary interest was whether there would be appparent sex differences in ‘emotionality’ and/or locomotion measures. Unlike domesticated species, females were found to ambulate and defecate more frequently than males in the OF. Both sexes increased their rates of defecation with exposure to the field. The running-wheel data indicatedf that overall males were more active, particularly during the dark phase of the light cycle. The data are examined with respect to similar measures obtained from domesticated laboratory rodents.     

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.     

An ethological analysis of open-field behavior in rats and mice

In our view open-field testing entails both a predatory encounter, which occurs as a consequence of handling and placement of subjects into the testing apparatus, and sudden social separation from conspecifics. We hypothesize, therefore, that open-field behavior represents a compromise between responses aimed at minimizing detectability as a predator evasion tactic, and those which are motivated by attempts to reinstate contact with companions. Six experiments were conducted using rats and mice to test various implications of this model. Pretest shock and the presence of a human observer each retarded the appearance of social reinstatement behaviors and enhanced responses which minimize detectability in both species. Likewise, because of diminished reinstatement tendencies animals tested in pairs froze longer than those tested individually. The applicability of this model to other aspects of open-field behavior in rodents was examined, and the contrast between this view and the general emotionality hypothesis was briefly discussed.     

Two Types of Strain Differences in Open-Field Behavior in Rats and their Mapping

Open-field behavior of three treatments for three strains of rats (SD, Long-Evans, Fischer-344) was plotted on a map by component scores that were derived from principal component analysis. The treatments consisted of electric shock, extensive stroking, or testing after habituation to the field. Five measures were used: ambulation, penetration into the inner square, rearing, defecation, and urination. There was a clear strain difference on the basis of a raw open-field test score. This was termed a raw-score strain difference. A treatment-effect strain difference, however, which is obtained by comparing treatment and control conditions, was not clear. Thus, the behavior of each treatment condition cohered clearly with each other on the map, regardless of raw-score strain differences. This indicates that the nature of emotional behavior caused by the present treatments is very similar among strains despite the clear raw-score strain difference.     

Personality in rats and pain measures

The pain threshold of rats previously selected according to ambulation and defecation scores was assessed. Ss were 89 Sprague-Dawley rats aged 90 days. They were submitted to a low-frightening open-field (LFOF) test and 40 rats were selected on the grounds of extreme ambulation and defecation scores. The pain threshold was then assessed in 10 daily tests during 2 consecutive days. The mean of the 20 tests was used as the measure of the threshold and the mean of the two most extreme values was used as the measure for pain tolerance. The results obtained show that the pain thresholds of high-defecatory rats are significantly lower than those of low-defecatory rats. A similar relationship is found between low- and high-ambulatory rats, but the differences do not reach statistical significance. When the results of all 4 groups are compared the low-ambulatory and high-defecatory rats (introvert-neurotic) show the lowest threshold value, and the high-ambulatory and low-defecatory rats (extravert-stable) show the highest one which is significantly different from any other group. The results obtained with respect to the tolerance threshold, in spite of the lack of statistical significance, follow the same direction as those shown by the pain threshold.     

An ACTH4-9 analog (ORG 2766) speeds recovery from septal hyperemotionality in the rat

The amount of hyperemotionality initially demonstrated after septal area lesions was reduced, and the rate at which the hyperemotionality attenuated over repeated testing, was enhanced by the administration of an ACTH4-9 analog, ORG 2766. This ACTH fragment was given for 4 consecutive days after surgery but terminated before testing began. Two weeks after the daily tests of emotionality, the animals were trained in a two-way active avoidance task. The typical increase in avoidance behavior seen in animals with septal lesions was observed in the lesioned animals tested with ORG 2766, but the usual high number of intertrial responses was greatly reduced in these animals. The results indicate that even after a brief series of ORG 2766 administration, there are changes in emotionality that may last for an extended period of time after the cessation of treatment.     

BEHAVIOUR OF RATS UNDER THE INFLUENCE OF ETHYL ALCOHOL IN AN OPEN-FIELD SITUATION

In a standardized open-field test, ambulation, defecation, time of non-locomotor activity, time spent motionless, preening, and rearing were recorded. Inter-observer differences were small. Test repetition caused significant behavioural changes. Different rats were used for each of five doses of alcohol (0.5–2 mg/g). The lowest dose (0.75 mg/g) affecting behaviour significantly increased time motionless, decreased non-locomotor activity, and depressed preening. Ambulation was the last sensitive measure of behaviour. The results suggest that arousal mechanisms are particularly sensitive to alcohol. The procedure seems useful for studies of effects of small doses of alcohol.     

Neonatal amphetamine exposure and hippocampus-mediated behaviors

Previous studies linking amphetamine use during pregnancy to changes in the behavioral development of affected infants have greatly increased society’s level of concern regarding amphetamine use by women of reproductive age. The aim of this study was to investigate whether exposure to d-amphetamine sulfate during the brain growth spurt, the most dynamic period of brain development, alters hippocampus-mediated behaviors during both pre-adolescence and young adulthood. Sprague–Dawley rat pups were intragastrically administered a milk formula containing 0, 5, 15 or 25 mg/kg/day of amphetamine from postnatal day (PD) 4–9. Following weaning, the effects of neonatal amphetamine exposure on hippocampus-mediated behaviors were assessed using the open-field, the water maze, and the conditioned taste aversion behavioral tasks. Results from these behavioral tests revealed that while amphetamine exposure during the brain growth spurt alters behaviors in open-field testing, it does not interfere with performance in either the water maze or the conditioned taste aversion paradigm. These results offer speculation that the effects of neonatal amphetamine exposure on hippocampus-mediated behaviors may be related to interactions between the “temporal” (time of drug exposure) and “regional” (different regions of the hippocampus) vulnerability issues.     

The development of territorial-induced intermale agonistic behavior in albino laboratory mice

Male mice of the CF-1 strain (Mus musculus) were allowed to take up lone residence in a small territory consisting of a 60-cm enclosure attached by a tubular runway to a standard mouse cage with food, water, and bedding. A group of ten mice, each of which resided in its own separate enclosure for 24 hours, were more aggressive toward intruders than other groups of ten mice following six-hour residence periods, or no such residence. Aggression toward intruders increased in repeated weekly tests of the six-hour residents, but after four weeks of testing did not reach the maximum stable level displayed by the 24-hour residents over four weeks of testing. In another experiment, the 24-hour residence period of groups of 20 CF-1 male mice was disturbed by briefly removing the mouse from the enclosure, before introducing the intruder, at various intervals prior to testing. Removal of the resident five minutes before testing resulted in a marked decrease in aggression toward intruders. Although lesser decreases in aggression followed intervals of 30, 45, and 60 minutes, a 180 minute interval resulted in no appreciable effects compared to undisturbed controls. It is concluded that exposure to the stimuli provided by the enclosure results in an aggressive readiness in the resident mouse which reaches a high level within a 24-hour period.     

Operant conditioning of large magnitude, 12-hour duration,heart rate elevations in the baboon

Two baboons were prepared with arterial and venous catheters and their heart rate and blood pressure were monitored continuously thereafter. Following a 2 to 3 week interval during which baseline cardiovascular levels were determined, the animals were exposed to daily 12 hr conditioning sessions (alternating with 12-hr “rest” or “Conditioning Off’ sessions) during which food reward and shockavoidance were programmed as contingent consequences of pre-specified increases in heart rate. Initially, the criterion heart rate was set at 10–15 bpm above the animal’s pre-experimental resting baseline level, with progressive increases programmed to occur at a rate approximating 7 bpm per week over a period of 8–10 weeks. Within this 2–3 month interval, heart rate doubled, reaching levels maintained above 160 bpm for more than 95 per cent of each daily 12-hour “Conditioning On” period. Propranolol selectively eliminated the conditioned heart rate increase but not the blood pressure elevation, indicating the contribution of sympathetic nervous activity to these operantly conditioned cardiovascular changes.     

Gastric ulceration and adrenocortical activity after inescapable and escapable pre-shock in rats

Two experiments are reported which investigated the effects of pre-shock treatment in rats on adrenocortical activity and susceptibility to later restraint-induced ulceration. In Experiment I, animals were exposed to a single inescapable 3 minute shock on 5 consecutive days. These shocked animals exhibited sensitisation of the adrenocortical response over days, increased adrenocortical reactivity to open field testing one week later and a trend for more severe ulceration after 20 hours of restraint. In Experiment II, animals were given 20 escapable or yoked pre-shock trials on 5 consecutive days. No sensitisation of the adrenocortical response was observed. Escape animals however were found to exhibit less gastric ulceration and a reduced adrenocortical responses after 20 hours of restraint 9 days after the last preshock session.     

Mapping Open-Field Behavior in Rats: Applicability Across Sexes

Open-field behavior of female and male Sprague-Dawley rats was plotted on a map using scores derived from a principal-component analysis. As reference points on the map, three treatment conditions were used: electric shock, extensive stroking, and additional trials after habituation to the field. Five measures were used: ambulation, penetration into the inner square, rearing, defecation, and urination. The behaviors in each treatment condition clearly cohered with each other on the map, regardless of sex difference in raw scores. This coherence shows that the nature of the emotional behavior caused by the present treatments is similar across sexes, indicating, to some degree, the applicability of the map across the sexes. The additional experiment (concerning the estrus effect on the open-field behavior) suggests that the estrus effect is not large enough to compromise the validity of the map, which was constructed on the basis of the data without control of the estrus effect.     

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.     

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.     

Speed of emotional information processing and emotional intelligence

The present study aimed to investigate the relationship between the speed of emotional information processing and emotional intelligence (EI). To evaluate individual differences in the speed of emotional information processing, a recognition memory task consisted of two subtests similar in design but differing in the emotionality of the stimuli. The first subtest required judgment about whether an emotional facial expression in the test face was identical to one of the four emotional expressions of the same individual previously presented. The second subtest required deciding whether the test face with a neutral emotional expression was identical to one of the four neutral faces of different individuals previously presented. Mean response latencies were calculated for “Yes” and “No” responses. All latencies were correlated with other measures of processing speed such as discrimination time and time of figure recognition. However, the emotional expression recognition subtest was hypothesized to require the processing of emotional information in addition to that of facial identity. Latencies in this subtest were longer than those in the face recognition subtest. To obtain a measure of the additional processing that was called for by the emotionality of the stimuli, a subtraction method and regression analysis were employed. In both cases, measures calculated for “No” responses were related to ability EI, as assessed via a self‐report questionnaire. According to structural equation modeling, there was a moderately negative association between latent EI and the latency of “No” responses in the subtest with emotional stimuli. These relationships were not observed for “Yes” responses in the same subtest or for responses in the subtest with neutral face stimuli. Although the differences between “Yes” and “No” responses in their associations with EI require further investigation, the results suggest that, in general, individuals with higher EI are also more efficient in the processing of emotional information.     

Effects of early exposure to ventral gland odor on physical and behavioral development and adult social behavior in Mongolian gerbils.

Comparisons were made between male and female gerbils reared by ventral gland-excised and intact patents. Repeated measurements before and after puberty failed to reveal an effect of gland odor exposure on body weight, ventral gland size, open-field defecation, and time of vaginal opening. Exposed animals were more attracted than nonexposed animals to a strange male's gland odor during preference tests involving "marked" and "unmarked" paper strips. Opposite-sex pairs of exposed animals engaged in more social behavior than did nonexposed pairs, but there was no difference in fighting frequency or, during extended cohabiitation, in fecundity. While early exposure to gland odor apparently does not affect physical maturation, it may enhance later responsiveness to stimuli (gland odors) that are useful in locating conspecifics and that facilitate social interactions between previously unacquainted gerbils.