Social interaction between drugged and undrugged rats

Behavioral mirroring in Wistar rats investigated through temporal pattern analysis

The study of social interactions lies at the core of several disciplines such as psychiatry, psychology and ethology, just to name a few. In this context, understanding the temporal patterns underlying interactive behaviors is of crucial importance. Here, we employed T-pattern detection and analysis to study social interactions in ten pairs of Wistar rats tested in an Open-Field environment. We found four different categories of interactive behaviors. One of them was of particular interest to us because it consisted of behavioral events that, taken individually, should not underlie an interaction of any kind; however, they were included in T-patterns, which is suggestive of a dyadic temporal coordination in the behavioral expression of two individuals. Within this category, we described for the first time a new subcategory of apparent interaction patterns characterized by events that one of the two rats repeats only if previously produced by the partner (i.e., behavioral mirroring). These findings are discussed in functional terms for rodents and in light of our current understanding of social interactions in humans.

Social Interaction Test between a Rat and a Robot: A Pilot Study

The social interaction test is based on spontaneous behaviour observed between pairs of animals, usually rodents. Commonly, the behaviour of one of the members in the dyad is related to the behaviour of its partner; therefore, making accurate predictions about behaviour is difficult, and the behaviour of the dyad cannot be controlled. In the present study, we programmed an e-puck robot with simple behavioural patterns, such as moving around a cage and following and approaching a rat. The results were analysed by comparing behaviour that was displayed by two groups of experimental rats towards different types of partners: (i) in the first group of experimental rats, they interacted with another group of rats and (ii) in the second group of experimental rats, they interacted with the e-puck robot.

Our aim was to study the behaviour of experimental rats in the social interaction test when the interaction partner is a pre-programmed robot, in order to find out whether a rat is able to display social interaction activities in that context. Those activities were evaluated by a structured scheme of possible behaviours, quantified in categories according to currently well-accepted nomenclature and definitions. In order to achieve this goal, we compared the social and non-social behaviour displayed by the experimental rat in rat-rat and rat-robot interactions (such as approaching and following behaviour). We observed predominantly non-social behaviours, such as exploring the cage, when the experimental rats confronted either another rat or the robot. The experimental rats displayed similar periods of approaching, sniffing and crawling (social behaviour), exploring, being quiet, self-grooming and evading (non-social behaviour) in encountering both the rat and the robot. However, in the presence of the robot, the experimental rats displayed long periods of time spent in following, in contrast to short periods of immobility. In the present study, we explored a behavioural repertoire that was classified into the social and the non-social, in which the robot was usually able to elicit social behaviour from the rat. The results of our experiments open possibilities for additional studies on social interaction in robot-live rat dyads (e.g., in predator-prey models).

Acute prosocial effects of oxytocin and vasopressin when given alone or in combination with 3,4-methylenedioxymethamphetamine in rats: involvement of the V1A receptor

The neuropeptides oxytocin (OT) and vasopressin (AVP) are recognized for their modulation of social processes in humans when delivered peripherally. However, there is surprisingly little evidence for acute social effects of peripherally administered OT or AVP in animal models. On the other hand, the party drug 3,4-methylenedioxymethamphetamine (MDMA, 'Ecstasy') has powerful prosocial effects in rats that appear to occur through stimulation of central OT release. Here, we directly compared the social effects of peripherally administered OT and AVP with those of MDMA, and examined a possible role for the vasopressin 1A receptor (V1AR) in the observed prosocial effects. Adult male Long-Evans rats were tested in a social interaction paradigm after OT (0.1, 0.25, 0.5, and 1 mg/kg, intraperitoneal (IP)), AVP (0.001, 0.0025, 0.005, 0.01, and 0.1 mg/kg, IP), and MDMA (2.5, 5 mg/kg, IP), or combined low doses of OT and MDMA, or AVP and MDMA. The effects of pretreatment with the non-peptide OT receptor antagonist compound 25 (C25; 5 mg/kg, IP) and the V1AR antagonist SR49059 (1 mg/kg, IP) were also examined. OT (0.5 mg/kg), AVP (0.01 mg/kg), and MDMA (5 mg/kg) potently increased 'adjacent lying', where rats meeting for the first time lie passively next to each other. C25 did not inhibit adjacent lying induced by OT, whereas SR49059 inhibited adjacent lying induced by MDMA (5 mg/kg), OT (0.5 mg/kg), and AVP (0.01 mg/kg). Interestingly, when ineffective doses of OT and MDMA, or AVP and MDMA, were combined, a robust increase in adjacent lying was observed. These results show for the first time acute prosocial effects of peripherally injected OT and AVP in laboratory rats, and suggest a commonality of action of OT, AVP, and MDMA in stimulating social behavior that involves V1ARs.

Sharing of the home base: a social test in rats

The open field provides abundant opportunities for a pair of rats to express social interactions. Rats demonstrate social proximity while exploring the open field and also during simultaneous occupancy of a home base (HB). The HB is defined as a place in the field for which rats show a long-term preference, both in terms of occupancy and as a starting and ending point of exploratory excursions. In the present study, the social proximity of pairs of rats treated with phencyclidine (PCP; 2 mg/kg) or saline (Sal), and rats treated with clozapine (CLZ; 1.3 mg/kg) alone or in combination with PCP (CLZ-PCP), was videotaped and analysed algorithmically. PCP was tested for its disruptive effects on social interactions, and CLZ was tested for its ability to reverse some forms of the disruptive effects of PCP. The results showed that PCP reduced the rate of pairs establishing a common HB and shortened social HB occupancy, but had no effect on episodes of social exploration in the field. These findings demonstrate that the antisocial effect of PCP cannot be generalized across the entire spectrum of behavioural states in the open field. CLZ further decreased rather than increased social HB occupancy. This effect was derived from the reduction in rate of pairs establishing a common HB.

Social isolation modifies nicotine's effects in animal tests of anxiety

1. These experiments determined whether the housing conditions of rats influenced the effects of nicotine in two animal tests of anxiety, social interaction and elevated plus-maze tests. 2. In animals housed singly for 7 days, (-)nicotine (0.025 mg kg(-1) s.c.) was ineffective, but 0.05, 0.1 and 0.25 mg kg(-1) (s.c.) significantly increased the time spent in social interaction, without changing locomotor activity, thus indicating anxiolytic actions. (-)Nicotine (0.45 mg kg(-1) s.c.) significantly reduced social interaction, indicating an anxiogenic effect. 3. However, in group-housed animals, (-)nicotine (0.025 mg kg(-1) s.c.) had a significant anxiolytic effect in the social interaction test, but 0.01, 0.05, 0.1, 0.25 and 0.45 mg kg(-1) were ineffective. (-)Nicotine (1 mg kg(-1)) reduced motor activity and social interaction in the group-housed animals. 4. In the elevated plus-maze, the time-course and the dose-response curve to nicotine were investigated. In both singly- and group-housed rats, (-) nicotine (0.1 - 0.45 mg kg(-1) s.c.) decreased the per cent entries into, and per cent time spent on, the open arms, indicating anxiogenic effects. 5. The housing condition influenced the time course, with significant effects at 5 and 30 min after injection in group-housed rats, and significant effects at 30 and 60 min in singly-housed rats. 6. In the social interaction test there was no difference in the scores of the first and last rats removed from group cages, whereas the order of removal from the cages did affect the scores in the elevated plus-maze. 7. These results provide further evidence that the two animal tests model distinct states of anxiety, and show how social isolation powerfully modifies both anxiolytic and anxiogenic effects of nicotine.

Recent developments in anxiety, stress, and depression

Recent research in the development, analysis, and pharmacology of animal tests of state anxiety is discussed, including the use of responses to predator odours, the role of learning in modifying the anxiety measured in the plus-maze, and the roles of cholinergic, NMDA, and dopaminergic systems. Developmental and genetic factors are considered with particular reference to the development of tests of trait anxiety. The roles of 5-HT1A receptors in anxiety, depression, impulsivitity, and agonistic behaviours are discussed. Recent studies on the impacts of stress on neurotransmitter, endocrine, and immune systems and the interactions between these systems are discussed, with particular emphasis on their contributions to the development of pathologic states relevant to anxiety and depression.

Automation of the social interaction test by a video-tracking system: behavioural effects of repeated phencyclidine treatment

The social interaction test is a valuable behavioural model for testing anxiolytic and neuroleptic drugs. The test quantifies the level of social behaviour between pairs of rats and it is usually based on manual analysis of behaviour. Advances in computer technology have made it possible to track the movements of pairs of rats in an arena, and the present paper describes the automation of the social interaction test by the commercial video-tracking programme, the EthoVision system. The ability of the automated system to correctly measure the social behaviour of rats is demonstrated by determining a dose-response relationship in the social interaction test for phencyclidine, a psychotomimetic drug that reduces social behaviour between pairs of rats. These data are subsequently analysed by the manual and automated data-acquisition methods and the results are compared. The study shows that the automated data-acquisition method best describes the behavioural effects of phencyclidine in the social interaction test by the locomotor activity of the rats, how much time the rats spend in different sections of the testing arena, and the level of social behaviour. Correlation analysis of the results from the manual and automated data-acquisition methods shows that the social behaviour measured by the automated system corresponds correctly to the social behaviour measured by the manual analysis. The present study has shown that the automated data-acquisition method can quantify locomotor activity, how rats use a testing arena and the level of social behaviour between rats in the social interaction test. The system cannot distinguish between social and aggressive behaviours, and therefore the rats should be tested in an unfamiliar arena to reduce territorial behaviour. Taking this limitation into consideration, the social interaction test can be automated by this computer-based video-tracking system and can be used as a routine test for quantifying the effects of drugs on the social behaviour of rats.

The MSH/ACTH(4-9) analog Org2766 counteracts isolation-induced enhanced social behavior via the amygdala

MSH/ACTH-like peptides influence social behavior induced by isolation It has been previously demonstrated that changes in locomotor activity as a result of isolation can be counteracted by Org2766 via the amygdala. The present study investigates whether isolation-induced changes in social behavior can also be affected by this peptide via the amygdala. A fully automated observation system was applied for detailed registration and analysis of movements of group-housed and 7-day isolated rats in a social interaction test. Administration of the MSH/ACTH(4-9) analog into the central nucleus of the amygdala elicited decreased locomotion, approach, and avoidance behaviors after isolation as compared to placebo-treated controls. However, general activity and social interest of group-housed rats were not affected by the MSH/ACTH(4-9) fragment. It is hypothesized that the amygdala is a site of action for neuropeptides in modulating social behavior.

Acute and chronic antidepressant drug treatments induce opposite effects in the social behaviour of rats

Clinical studies indicate that the behavioural responses/reactions of depressed patients to environmental and social stimulation are modified during remission from depressive illness, and require continuous (at least 3 weeks) drug treatment. In order to determine whether antidepressant drugs modify the behavioural patterns of experimental animals in ways that may be related to their ability to modify human reactive behaviour, we have examined the effects of acute and chronic treatment with clomipramine, fluoxetine, iprindole, mianserin and phenelzine (antidepressants with markedly different acute pharmacology) on the behaviour exhibited by rats during social interaction (SI). Acute treatment of short-term isolated resident rats with non-sedative doses of each antidepressant drug selectively and dose-relatedly reduced aggressive behaviour exhibited during SI. Conversely, haloperidol (antipsychotic) or diazepam (anxiolytic) only reduced aggressive behaviour at sedative doses. In comparison, following chronic treatment, all antidepressants examined, but not haloperidol or diazepam, increased aggressive behaviour exhibited by resident rats during SI which returned to the pre-treatment level by 7 or (after phenelzine) 14 days after the cessation of treatment. It is concluded that the antidepressants examined induce selective, diametrically opposite effects on rodent aggressive behaviour following acute and chronic treatment which is indicative of antidepressant efficacy. Furthermore, it is argued that the increased aggressive behaviour following chronic antidepressant drug treatment may indicate a disinhibition of social behaviour in the rat that mirrors the externalization of emotions associated with the remission of depressive illness.

Social isolation and cohabitation with haloperidol-treated partners: effect on density of striatal dopamine D2 receptors in the developing rat brain

The influence of the social environment on striatal dopamine D2 receptor density in the developing rat brain was investigated. Social isolation of rats from 20 to 60 days of age was associated with a decrease in the density of striatal dopamine receptors. Daily handling of the animals did not attenuate this effect. Chronic haloperidol treatment increased striatal dopamine receptor density to normal control values. Cohabitation with haloperidol-treated rats from 20 to 60 days of age was also associated with a decrease in the density of striatal dopamine D2 receptors in nondrugged animals similar to that seen in animals housed in isolation. The contribution of early life experiences to the development of normal receptor functioning is discussed.

Social play in juvenile rats: a decade of methodological and experimental research

The social play behavior of juvenile rats was originally described nearly a century ago, but research methods have only recently included the controlled laboratory investigation of psychobiological variables. This review covers the experimental literature of social play or play fighting behavior in juvenile laboratory rats reported during the last decade. Innovative measures for quantifying social play are described; hormonal, pharmacological, and neurological variables are examined; and interpretative concepts of social play are discussed. The current emphasis on measures and procedures as well as the limited scope of current research effort suggests a formative stage of research development.

Amphetamine-induced perseverative behavior in a radial arm maze following DSP4 or 6-OHDA pretreatment

Mice permitted to explore an 8-arm radial maze tended to visit those arms least recently entered. Treatment with D-amphetamine engendered a perseverative tendency, wherein mice repeatedly visited two arms of the maze. Administration of the norepinephrine (NE) neurotoxin, N-2-chloroethyl-N-ethyl-2-bromo-benzylamine (DSP4), appreciably reduced NE in the hippocampus and cortex, moderately reduced NE in the locus coeruleus, and had only a small effect on hypothalamic NE. The DSP4 treatment resulted in a decrease of locomotor activity among amphetamine-treated mice, coupled with an increase of stereotyped response patterns. Although the NE depletion did not affect the pattern of exploration that mice ordinarily displayed, DSP4 appreciably increased the perseverative tendency provoked by amphetamine. Reduction of dopamine (DA) and NE by intraventricular administration of the catecholamine neurotoxin, 6-hydroxydopamine (6-OHDA), antagonized the effects of amphetamine, such that the frequency of alternation responses was increased and the proportion of perseverative responses was reduced. The effectiveness of the 6-OHDA treatment in antagonizing the amphetamine-induced perseveration was not reduced among mice that were pretreated with desmethylimipramine, which resulted in partial prevention of the NE reduction by 6-OHDA administration. It is suggested that DA neuronal activity contributes to the amphetamine -provoked perseveration , whereas NE stimulation modifies the perseverative tendency by influencing exploration or habituation.

Changes in social behaviour of rats following chronic treatment with gamma-endorphin antiserum injected into the nucleus accumbens

Treatment with gamma-endorphin antiserum twice daily for 12 days, by injection into the nucleus accumbens did not change the basal level of social activity or explorative behaviour when pairs of rats were tested in a social interaction test. The decrease in social interactions due to increased light level as observed in placebo-treated rats, was not present in animals treated with gamma-endorphin antiserum. Significantly more freezing and fly-responses were observed in the rats treated with antiserum, as reactions to penetrating sound stimuli. These changed responses to light and sound stimuli persisted for at least 3 days following discontinuation of treatment. It is concluded that treatment with gamma-endorphin antiserum, injected into the nucleus accumbens results in disturbances in the integration of environmental stimuli in social behaviour and in enhanced responsiveness to stressful stimuli. It is suggested that these effects may be related to increased dopaminergic transmission in some dopaminergic systems in the nucleus accumbens, implicating these systems in the environmental control over social behaviour.

Short-term isolation increases social interactions of male rats: a parametric analysis

Frequencies of social interactions were higher in pairs of short-term individually housed male Wistar rats as compared to group-housed animals. This was most pronounced when an individually housed rat and a group-housed conspecific were tested together in the morning under red light conditions. Then, in particular the behavioral elements exploration partner, anogenital investigation, crawl over/mount and social grooming were enhanced. The increases in social interactions was dependent on the duration of the period of individual housing and appeared to be maximal after 4 to 7 days of individual housing. The effect extinguished after repeated testing. The observed behavioral changes were hardly affected by habituation to the test cage and were also present in young animals. The increase in social interactions is apparently not due to a general increase in locomotor or exploratory behavior, since no differences in ambulation between individually- and group-housed animals were observed when they were tested together in the social interaction test, and locomotor activities hardly differed in an open field test procedure.

The use of social interaction as a method for detecting anxiolytic activity of chlordiazepoxide-like drugs

The social interaction test in rats provides a method for detecting anxiolytic activity that does not use food or water deprivation, or electric shock, and therefore obviates difficulties of interpretation that might arise from drug-induced changes in motivation. Since social interaction is measured under more than one test condition any overall increase or decrease in social behaviour can be detected independently from the drug x test condition interaction that characterizes an anxiolytic drug. The Geller-Seifter conflict test was designed with two schedules of reinforcement for the same reasons. Any candidate test for anxiolytic action that examines drug effects under only one experimental condition is open to misinterpretation and may also prove unreliable if the critical experimental factors ( e.g. the level of food deprivation or the shock intensity) are changed. The testing procedure in the social interaction test is relatively time consuming in terms of observer-hours, but no lengthy pretraining of the animals is required. There is no way of fully automating the scoring and therefore it is important that the observers do not know the experimental group of the rats that they are scoring, and that tape recordings are made so that the scores can be checked. It has not so far been fruitful to analyze drug effects on every individual social behaviour, but this method does allow changes in individual behaviours to be detected. By entering the data directly into a computer we are now able to store the frequency and duration of each behaviour as well as the sequence of behaviours. It will then be possible to determine whether a detailed analysis of drug effects on the patterning of social behaviours will prove a useful addition to the social interaction test

Acute and chronic effects of three benzodiazepines in the social interaction anxiety test in mice

The effects on active social interaction of acute and chronic dosage with diazepam (1 mg/kg), desmethyldiazepam (2 mg/kg), and chlor-desmethyl-diazepam (0.125 mg/kg) were studied in pairs of mice. The mice were tested under either high or low levels of illumination. In all cases acute drug treatment significantly reduced social interaction, but this was not seen with chronic treatment (9 days). Two of the drugs, diazepam and desmethyldiazepam, showed an anxiolytic action, i.e., these drugs resulted in significantly less variation in social interaction with the change in light levels, compared with vehicle-injected controls.

Can social interaction be used to measure anxiety?

1 Pairs of male rats were placed in a test box for 10 min and the time they spent in active social interaction was scored. Maximum active interaction was found when the rats were tested under low light in a box with which they were familiar. When the light level was increased or when the box was unfamiliar active social interaction decreased. 2 Exploration (time spent sniffing objects) decreased in the same way in relation to test conditions as did social interaction. As these decreased, defecation, and freezing increased. 3 Anosmic controls showed that the decrease in social interaction across test conditions could not be attributed to olfactory changes in the partner. 4 Chlordiazepoxide (5 mg/kg) given chronically prevented or significantly reduced the decrease in social interaction that occurred in undrugged rats as the light level or the unfamiliarity of the test box was increased. Controls showed that this effect could not be entirely attributed to chlordiazepoxide acting selectively to increase low levels of responding. 5 The effect of chronic chlordiazepoxide contrasts with its action when given acutely; in the latter case it has only sedative effects. 6 Whether this test can be used as an animal model of anxiety is discussed and this test is compared with existing tests of anxiety.

Drug-induced changes in the maternal behavior of rats

The effect of chlorpromazine and amphetamine (3 mg/kg b.w. injected s.c.) on the maternal behavior of rats was observed on days 4, 5, 6, 8, and 10 after the birth of the young. Spontaneous behavior in the presence of the young and contacts with them were recorded in four different testing situations. Both drugs interfered with the maternal behavior of female rats and reduced the duration of contacts with the young. The level of behavioral manifestations depended on the type of experimental procedure.