Isolation distress and maternal comfort responses of two-week-old rat pups reared in social isolation

In 2-week-old rats, isolation from social companions in an unfamiliar place elicits ultrasonic vocalization rearing and locomotor behavior. These responses are prevented and close body contact is maintained if littermates or the dam are present. It has generally been believed that such isolation distress and comfort responses develop as a result of prior social experience. We reared pups in isolation from the third postnatal day and found essentially normal responses. A second experiment replicated and extended these results to pups reared in isolation from the day of birth. Isolation-reared pups did have higher levels of ultrasonic vocalization than their normally reared littermates, lower body weight, and lower post-test temperatures. We conclude that a lengthy period of close body contact and frequent social interactions with conspecifics are not necessary for the development of attachment responses in this species.     

Acquisition of schedule-induced polydipsia in rats with no prior drinking experience

Three litters of 10 rat pups each were reared on Purina laboratory chow and either (1) continuous access to water, (2) access to both water and lettuce until weaning at 21 days and then only lettuce, or (3) continuous access to lettuce. At 100 days all rats were reduced to 80% free feeding weight and tested for polydipsia. During 15 sessions of polydipsia testing, excessive postpellet drinking developed in all groups to 45 mg Noyes pellets delivered on a fixed-time 1 min schedule. No significant differences in water intake over sessions were found among groups. It was concluded that schedule-induced polydipsia does not represent an exaggeration of a learned prandial drinking pattern, but rather an exaggeration of an inborn prandial drinking reflex.     

Mouse killing, insect predation, and conspecific attack by rats with differing prior aggressive experience

Mouse-killing, cockroach predation, and conspecific attack were examined in male Long-Evans rats with a history of intraspecific aggression (n = 20), defeat (n = 20), or no aggressive experience (n = 20). Roaches were more likely to be attacked during 30 min tests, and were attacked more rapidly than mice or rats regardless of previous social experience of subjects. Rats with aggressive experience attacked conspecifics more readily than subjects with defeat or no experience. There was no effect of prior experience on mouse-killing. These results indicate that mouse-killing does not correspond closely to either predation or intraspecific attack.     

Fostering secure attachment: experiences of animal companions in the foster home

This study sought to use attachment theory as a lens through which to explore children’s relationships with animal companions in the context of long-term foster care. Inductive and deductive thematic analyses of longitudinal case study data from eight children and their foster families suggested (a) that children’s relationships with animal companions satisfied attachment-related functions in their own right and (b) that animal companions also helped to soften perceptions of foster caregivers, facilitating opportunities for the development of closeness. Animals in the foster home may therefore play an important part in helping children to find and develop secure, warm, and loving relationships.     

The effects of stress on play and home cage behaviors in adolescent male rats

One prominent feature of adolescence is the high frequency of social behaviors, such as play. Engaging in these behaviors appears necessary for proper socio‐emotional development as social isolation during adolescence typically leads to behavioral dysfunctions in adulthood. The present experiments examined the effects of stress on social and nonsocial behaviors in group housed adolescent male rats. We found that acute restraint stress led to a complete inhibition of play (e.g., nape contacts and pins) and reduced social investigations in pre‐ (28 days), mid‐ (35 days), and late‐adolescent (42 and 49 days) animals. A follow‐up study, however, found that restraint‐induced suppression of play and social investigations was transient such that experimental animals engage in these behaviors at levels similar to those of controls 1 hr after termination of the stressor. We also found that exposure to repeated restraint stress throughout adolescence led to a decrease in social investigations, while leaving play largely unaffected. Interestingly, in all of the experiments, nonsocial behaviors (e.g., eating, drinking, grooming) were unaffected by restraint, suggesting these effects of stress are specific to social behaviors. Together, these data indicate that both acute and repeated stress significantly affect social behaviors during adolescence. © 2009 Wiley Periodicals, Inc. Dev Psychobiol 52: 62–70, 2010     

Postweaning social experience and adult aggression in rats

One group of male rats was reared continuously in small, stable colonies of three animals each during a ten-week period beginning when they were 46 days old. A second group of animals was also reared in small groups of three animals each but membership within these colonies was randomly changed at weekly intervals. Thereafter, all subjects were housed in individual cages. A 24 hr test of the subjects' aggression toward an unfamiliar male conspecific at 130-133 days of age indicated that only the heaviest animal in each of the stable colonies was aggressive. In contrast, all animals in the random-composition group were aggressive toward intruders. Scores on a second test of intruder-directed aggression administered when the subjects were nine months old were significantly related to scores on the first aggression test. Subtle variations in social experience during development are critical in establishing long-term patterns of aggression toward conspecifics in laboratory rats.     

Physiological and behavioral effects of different success during social confrontation in pigs with prior dominance experience

The impact of a 10-h social confrontation on behavior, plasma adrenaline, noradrenaline and cortisol was studied in 14 domestic pigs (eight castrated males and six females) with prior dominance experience. Prior to the experiments, animal groups, each consisting of nine growing pigs (12 weeks old) from different litters, were composed randomly. After 5 days, the pig with the highest rank from each group was removed, provided with a jugular vein catheter and kept in single housing for 2-3 weeks. After this period, each test animal was returned into its familiar group for a 10-h social confrontation. The reintroduction of the test animals into the familiar groups caused frequent agonistic interactions during the first 30 min. Seven animals succeeded to win most of their encounters during the confrontation test and were classified as High Success (HS) animals, whereas seven other animals lost most of their encounters and were classified as Low Success (LS) animals. The reintroduction of the test animals into the groups provoked also marked changes in behavioral and physiological measures. The frequent fighting behavior during the first 30 min was accompanied by a rapid increase of plasma catecholamines and a delayed increase of cortisol. Immediately after introduction, LS pigs tended to show higher plasma adrenaline and noradrenaline concentrations than HS pigs. There was also a tendency for a sustained increase of noradrenaline/adrenaline ratios in HS pigs, whereas the ratios of LS pigs remained nearly unchanged. No significant differences between both groups were found in cortisol levels and in the frequency of agonistic interactions. However, LS animals showed less locomotion, more lying and spent less time exploring the pen or other animals. These results show that during a social confrontation the experience of defeats for formerly high-ranking pigs is accompanied by increased submissive or passive behavior and a higher sympathoneural and adrenomedullary reaction, which may indicate more emotional distress and fear compared to successful animals.     

Shock-induced fighting attenuates the effects of prior shock experience in rats

We compared the responses of animals exposed singly to inescapable shock with those of animals exposed to the same shock in pairs and thus able to fight in response to shock. During the shock sessions animals shocked in pairs showed a reduced ACTH response when compared with animals shocked individually, and the reduction in ACTH was not dependent on the amount of fighting which occurred. In addition, if animals had previous opportunities to fight, the response to shock was still attenuated even when the partner was no longer present. When subsequently tested in a novel task it was observed that fighters, like controls, showed a reduced pituitary-adrenal response to novelty when a consummatory response was available. Singly shocked animals, however, exhibited elevated levels of plasma corticosterone whether or not they could drink in the novel chamber. We hypothesized that fighting is a consummatory response, and that the reinforcement provided by performance of this consummatory response reduced the ACTH response to shock and permanently altered subsequent responsiveness.     

Relative importance of experience, social facilitation, and availability of milk in weaning of rats

These studies investigated the role that social facilitation, availability of the dam, and milk play in the maintenance of suckling behavior. Beginning at Day 20, rat pups' suckling experiences were restricted to testing with an anesthetized dam. In the first experiment, nipple attachment was abandoned by about Day 25 in rats that were tested alone with an anesthetized dam for 1 hr per day. When tested in groups of four, nipple attachment was maintained until about Day 27. Increasing exposure to an anesthetized dam to 2 hr per day prolonged nipple attachment about another 4 days. In the second experiment, pups were given either one or two daily 1-hr attachment tests and tested with either an anesthetized dam or an anesthetized dam in which the milk letdown reflex was reinstated. Both increasing the daily exposure to an anesthetized dam and reinstating milk letdown significantly prolonged suckling. Pups given two daily exposures to an anesthetized, milk-laden dam attached until about Day 47, long past the normal age of weaning.     

Psychological distress and work and home roles: a focus on socio-economic differences in distress

BACKGROUND: Home and work factors have been linked to psychological status, but less is known about their contribution to social inequalities in psychological status. We examine whether social inequalities in psychological distress can be explained by work-home factors and whether the impact of these potential explanatory factors is similar for men and women. METHODS: Data are from the 1958 British birth cohort study. We sought to explain social class differences in psychological distress at age 33. Explanatory factors were classified as work-home roles: i.e. employment, marital status, domestic responsibility, children and elderly care; and work-home characteristics: i.e. job-strain, insecurity, unsocial working hours, youngest child's age, number of children and level of involvement in childcare. RESULTS: A social gradient in psychological distress was found: odds ratios for classes IV and V v. I and II were 2.65 (men) and 3.02 (women). Work factors had consistently stronger associations with psychological distress and with social class among men than women. Work factors had a greater impact on class differences in psychological distress in men. Associations for home roles and characteristics were less consistent and their combined effect on class differences in distress was negligible for both sexes. CONCLUSION: Explanations for the social gradient differ for men and women. Work may be more important for men than women, but the impact of home factors was not strong during the early adulthood of this cohort.     

Psychological distress, life stressors, and social support in new immigrants with HIV

The expression of psychological distress is culture-dependent. Ethiopian Jewish immigrants' expression of distress is anchored in their unique culture. The authors' aim in this study was to assess the psychological distress of HIV-positive (HIV+) Ethiopian Jewish immigrants in Israel, using a culture-based tool, and to examine the relations of psychological distress, psychosocial variables, and T lymphocyte subset counts and viral load. Participants were 56 HIV+ patients. The authors assessed psychological distress by the self-report questionnaire, which they adjusted for the Ethiopian immigrants (SRQ-E). The authors also assessed adherence to treatment regimen, number of life stressors, and degree of perceived social support, T lymphocyte subset counts, and viral load in plasma. The overall level of psychological distress was in the high range of the SRQ-E scale and was considerably higher in men than in women. Psychological distress was related to more life stressors and lower perceived social support. Women reported having more social support, had better T(CD4+) lymphocyte count and T(CD4+)/T(CD8+) ratio, and lower viral load than did men. Better HIV indicators were related to shorter duration of HIV+ since diagnosis, better adherence, and more social support, but not to psychological distress. The culture-based tool allowed identification of the high degree of psychological distress among the HIV+ Ethiopian immigrants. Researchers need to assess the adaptability of culture-based questionnaires to determine psychological distress in HIV+ patients.     

Telemetric recording of sleep and home cage activity in mice

STUDY OBJECTIVES: This study assessed differences in spontaneous sleep and locomotor activity in inbred and hybrid mouse strains and evaluated telemetry for recording sleep in mice. DESIGN: Uninterrupted recordings of sleep and home cage activity were obtained in four mouse strains. Pre-operative and post-operative home cage activity was obtained in two strains. SETTINGS: N/A PARTICIPANTS: The subjects were mice of three inbred (C57BL/6J (B6), n=25; BALB/cJ (C), n=24; DBA/2J (D2), n=30) strains and one hybrid (CB6F1/J (CB6: C x B6), n=19) strain. INTERVENTIONS: Electroencephalogram (EEG) and activity were recorded by telemetry, and behavioral states were visually scored based on EEG and activity records. Home cage activity was determined utilizing photobeam interruptions. MEASUREMENTS AND RESULTS: 1) Among the three inbred strains: C mice had the least sleep and the greatest amount of activity; D2 mice exhibited the least non-rapid-eye-movement (NREM) sleep, the longest average NREM-bout length, and the greatest diurnal ratio of sleep and were the most inactive; B6 mice had the most sleep and an intermediate activity level; no differences among inbred strains were observed in total REM. The CB6 mice exhibited intermediate levels of total sleep and activity and had greater amounts of REM compared to its parental strains. 2) Total operative mortality was 9.3%, with all deaths occurring within 3 to 9 days after the operation; significant reductions in activity were observed after the operation. CONCLUSION: Differences in spontaneous sleep and activity exist among inbred and hybrid mouse strains. Accurate determination of sleep states in mice can be achieved with telemetrically recorded EEG and activity.     

The effect of home cage stimuli on acquisition and retention of an active avoidance response in previsual rats

The effect of home cage environmental stimuli on learning and the effects on retention of the presence or absence of these familiar contextual training stimuli during the retention test (Experiment 1) or during the retention interval (Experiment 2) were examined using 10-day-old rats, a multidirectional active avoidance task, and a 30-min retention interval. Home cage environmental stimuli were found to improve learning. A change in stimuli immediately after training, during the 30-min retention interval, was found to have a greater impact on retention performance than stimulus change introduced at the time of the retention test. The implications of these findings are discussed in relation to ontogenetic differences in retention performance and theories of forgetting.     

Interleukin-6 improves the survival of mesencephalic catecholaminergic and septal cholinergic neurons from postnatal, two-week-old rats in cultures

Interleukin-6 (human recombinant) supported the survival of cultured mesencephalic, catecholaminergic and septal cholinergic neurons from postnatal, two-week-old (P13-P15) rats. Significantly, more catecholaminergic neurons, stained by monoclonal anti-tyrosine hydroxylase antibody, were found in cultures supplemented with interleukin-6 at a concentration of 5 ng/ml than in cultures not treated with interleukin-6. The optimal dose used was 50 ng/ml. The survival effect of interleukin-6 on postnatal rat, tyrosine hydroxylase-positive neurons was observed both in cultures using serum-containing and serum-free medium. Contents of dopamine and noradrenaline in cultures with interleukin-6 were also larger than in control cultures. Interleukin-6 also increased the survival of cultured embryonic (E17) rat midbrain tyrosine hydroxylase-positive neurons. The effect on these neurons was, however, smaller, and the optimal dose of interleukin-6 was nearly 5 ng/ml. Interleukin-6 also supported the survival of cultured postnatal (P13) rat septal cholinergic neurons, visualized by acetylcholinesterase staining. The concomitant addition of mouse nerve growth factor (100 ng/ml) and interleukin-6 (50 ng/ml) had a synergetic effect on the survival of acetylcholinesterase-positive neurons in culture. Our data suggest that the survival of cultured tyrosine hydroxylase-positive, mesencephalic, and acetylcholinesterase-positive, septal neurons from postnatal two-week-old rats was supported by interleukin-6, just as there was a different dose dependency of interleukin-6 on the cultured postnatal neurons compared with embryonic neurons.     

Effects of prior experience with dehydration and water on the time course of dehydration-induced drinking in weanling rats

Although cellular dehydration increases oral responding and swallowing of orally infused water in rats as young as 2 days old, it is not until well after the time of weaning that dehydration stimulates immediate water-seeking and initiation of drinking in situations where the water source must be approached voluntarily. Recent work has shown that the goal-directed appetitive sequence for drinking-orienting, approaching, and initiating contact with water-matures much later than the more precocial oral licking and swallowing behaviors, and normally comes to be elicited by dehydration only after post-weaning experience with dry food. In the current experiments we evaluate some critical features of post-weaning experience with dehydration and drinking, and find that prior experience with initiating drinking while dehydrated, but not experience with dehydration nor water per se, alters the time course of water intake during a subsequent hydrational challenge. The effects of experience are manifested as an increased proportion of water consumed in the early portion of the test, rather than a general increase in total consumption. These findings are consistent with the interpretation that prior experience is necessary for the coordination of water-oriented appetitive behaviors that lead to the initiation and maintenance of drinking bouts, and provide further evidence for an associative learning account of the acquisition of dehydration-induced drinking.     

Anxiety in rhesus monkey infants in relation to interactions with their mother and other social companions.

In this study the anxiety-related components of rhesus monkey infant behavior at an early stage of social development were examined. Eight rhesus infants (age 30-40 weeks) belonging to 3 captive groups were administered with an anxiogenic drug (beta-CCE; 0.2 mg/kg) and an anxiolytic drug (midazolam; 0.2 mg/kg). Saline solution was used as placebo. All infants were tested twice with each drug (four times with placebo) and their behavioral interactions with their mother and other social companions were recorded in 1-hr observation sessions. No convulsant or sedative effects of the drugs were observed. beta-CCE was associated with an increase in time spent by the infant with its mother and a concomitant reduction in proximity with other individuals and in social play. Midazolam did not affect the mother-infant interaction but increased the infant's locomotor activity away from the mother and its proximity and social play with juveniles and subadults when compared to peers. These results suggest that, although infant anxiety can be experimentally induced, it is not a major component of the mother-infant relationship. Infant anxiety, however, might affect the formation of other social bonds and play a part in the development of avoidance responses toward other individuals.     

The experience and influence of social support and social dynamics on cardiovascular disease prevention in migrant Pakistani communities: A qualitative synthesis

Objective

The objective of this research was to synthesise qualitative literature about the perceived influence and experience of social support, in relation to cardiovascular disease (CVD) prevention in migrant Pakistani communities.