Escape versus exploratory activity: An interpretation of rats' behaviour in the open field and a light-dark preference test

To test the assumption that dark preference in rats can serve as a measure of emotionality, dark preference was compared with ambulation and defacation in the open field. One group of 80-days-old male rats was handled for seven days; another group remained undisturbed. All animals were tested on each of five successive days in both a light-dark preference situation and an open field. Handled rats ambulated more in the field and stayed less time in the dark than non-handled ones. Significant negative correlations were found for the different days between open field ambulation and dark preference. Correlations between dark preference and open field defacation were positive except on day one. From the first to the second trial dark preference increased in both groups while open field ambulation decreased. The results were considered to support the hypothesis of dark preference as a measure of emotionality.In a second study an investigation was made as to whether high initial activity in a new situation is brought about by exploration or by an escape tendency. Again one group of male albino rats was handled. During testing, half of the handled and half of the non-handled rats had the chance of escaping from the open field into the adjacent home cage. From there the animals had the possibility of re-entering the field. The second half of each group had to stay in the field. These latter animals showed a remarkable decrease in ambulation from the first to the second trial. Rats which had access to their home cages seldom re-entered the field in the first trial. In later trials, however, ambulation in the field increased. Non-handled rats needed more trials before they started investigating the field. It was concluded that this result gives more support to an explanation of initial activity in terms of escape behaviour.     

The reinforcing property and the rewarding aftereffect of wheel running in rats: a combination of two paradigms

Wheel running reinforces the behavior that generates it and produces a preference for the context that follows it. The goal of the present study was to demonstrate both of these effects in the same animals. Twelve male Wistar rats were first exposed to a fixed-interval 30 s schedule of wheel-running reinforcement. The operant was lever-pressing and the reinforcer was the opportunity to run for 45 s. Following this phase, the method of place conditioning was used to test for a rewarding aftereffect following operant sessions. On alternating days, half the rats responded for wheel-running reinforcement while the other half remained in their home cage. Upon completion of the wheel-running reinforcement sessions, rats that ran and rats that remained in their home cages were placed into a chamber of a conditioned place preference (CPP) apparatus for 30 min. Each animal received six pairings of a distinctive context with wheel running and six pairings of a different context with their home cage. On the test day, animals were free to move between the chambers for 10 min. Results showed a conditioned place preference for the context associated with wheel running; however, time spent in the context associated with running was not related to wheel-running rate, lever-pressing rate, or post-reinforcement pause duration.     

Cage size preference in rats in the laboratory

The size of an enclosure is an integral part of how well it accommodates a nonhuman animal's welfare; however, most enrichment studies concentrate on modifying the area inside the enclosure rather than enlarging it. It has been suggested that rats have little need for more cage space, but there is no empirical evidence about rats' need for space. This experiment provides preliminary evidence for the preferences of 5 male and 5 female albino rats using T-maze choices followed by 5 min dwelling times. The rats showed a moderate but significant preference for the larger of 2 cages [540 cm2 vs. 1,620 cm2; binomial z, p <.05]. When the rats shared the chosen cage with 4 familiar cage mates, their preference for the larger cage did not become any stronger [paired t[9] = -.820, p >.05]. The results suggest that rats should be given a somewhat larger space allowance but could share it with up to 4 other rats.     

The role of environmental familiarization in novel-object preference

The experiments in this report examined the behavioral variables modulating novel-object preference in a widely used 'object recognition' preparation. This preparation takes advantage of the tendency of rats to interact more with a novel than a familiar 'sample' object in a free-choice situation. Experiment 1 examined the interaction between environmental familiarization and the duration of sample-object exposure in the development of a novel-object preference. Interaction with the sample object during sample-object exposure was increased when rats were given time in the environment prior to presentation of the sample object. Also, provided that the sample-object exposure was greater than 2 min, rats given environmental familiarization time prior to sample-object exposure displayed a novel-object preference. Rats that received the same amount of sample-object exposure without prior exposure to the environment alone did not discriminate between the sample and novel object. In Experiments 2 and 3, sample-object exposure occurred in a different environment than the novel-object test. Novel-object preference was not affected regardless of whether that testing environment was familiar or novel. This result differs from previous work that finds that an object recovers some novelty when moved to a new spatial location.     

Response to novel object in Wistar and wild-type (WWCPS) rats

Laboratory rats react to a novel object with a rapid redirection of exploratory behaviour towards the source of the novelty and a subsequent decline of this neotic preference with repeated object exposure. Studies with wild Rattus norvegicus have shown that a novel object in a familiar cage results in avoidance reactions (neophobia) in those animals, but it is also well established that the wild R. norvegicus show strong aversive reactivity to a variety of high intensity stimuli. In this study we aimed to create low-stress conditions enabling the comparison of spontaneous exploratory behaviour directed at a novel object in male (age = 80 days) “wild-type” WWCPS rats (n = 21; fourth generation bred in captivity) and Wistar (n = 24) rats. The study involved repeated placing of individual animals in the experimental chamber for 15 (6 min) trials on consecutive days. On the 11th day the novel object was introduced. Animals were tested in darkness and without human presence. Under these conditions neither WWCPS nor Wistar have shown behavioural signs of high emotional arousal, both lines have shown comparable general levels of experimental cage exploration and the positive new object exploratory reaction was observed only in Wistar rats.     

The role of visual stimuli in the acquisition of place preference with morphine reinforcement]

In experiments with rats was studied the role of visual stimuli in conditioning of place preference in a T-shaped chamber, certain stimuli being combined with morphine injection (5 mg/kg). Intensity of illumination of the chamber sections, colour of walls, and the orientation of dark stripes on the walls were varied. Testing the animals' behaviour began with determining the reward properties of certain visual stimuli on the basis of the total time of the animals' stay in a chamber. Procedure of combining the visual stimuli with morphine was repeated four times. Associative properties of the stimuli were revealed by comparing the learning efficiency in different experimental groups. Learning within the framework of the place preference model was concluded to depend upon the reward properties of the visual stimuli, whereas the behaviour itself to be based on the mechanism of the instrumental but not the classical conditioned response.     

Object familiarization and novel-object preference in rats

We investigated whether object familiarization was related to novel-object preference in the novel-object preference (NOP) test in rats. In Experiment 1, we found that no significant correlation existed between the time spent investigating 2 identical copies of a sample object and the degree of preference for a novel object. In Experiment 2, rats investigated 2 identical sample objects for a total of 5, 30, 60, 90 or 120 s. Investigatory preference for the novel object was compared to chance expectancy as well as between the groups. Only the 90-s group and the 120-s group displayed above-chance investigatory preference for the novel object, but novel-object preference for these 2 groups did not differ from each other, suggesting that a minimal amount of sample object investigation is necessary for rats to develop a novel-object preference, beyond which no increase in novel-object preference was found. In Experiments 3 and 4, normal rats and rats with hippocampal lesions were given repeated test trials, with the same sample object presented with a different novel object, at 24-h and (Experiment 3) and 35-s intervals (Experiment 4). In both experiments, novel-object preference did not increase in magnitude with repeated sample object exposures, suggesting that increased familiarity with the sample object does not result in increased novel-object preference. Rats with lesions of the dorsal hippocampus showed an unreliable investigatory preference for the novel object. These results are discussed in terms of the potential limitations of the NOP test as a tool for the assessment of object-recognition memory in rats.     

Cage-change interval preference in mice

Before animal research facilities began using individually ventilated cage (IVC) systems for mice, cages were often changed one or more times per week. When using IVC systems, however, it is standard practice to change cages only once every 2-3 weeks. When deciding how often to change cages, personnel may consider the cost of labor needed to change the cage, as well as the cage type and bedding type, rather than animal preference or concern for animal well-being. The authors carried out a simple preference test in groups of mice. Mice were allowed to choose between an unsoiled cage and cages that had not been changed for 1 d, 7 d or 14 d. When evaluating where mice positioned their nests and the amount of time mice spent in the various cages, the authors found that the mice preferred the unsoiled cage. Younger mice (<150 d old) showed a stronger preference for the unsoiled cage than did older mice (>150 d old). Further studies are warranted to evaluate mice's preferences for cages changed at different intervals and to determine whether prolonging the interval between cage changes has any negative effects on mice.     

Conditioned place preference induced by sexual interaction in female rats.

The present study was undertaken to establish whether the conditioned place preference paradigm can be utilized to investigate and elucidate the neuroendocrine basis of the appetitive elements of female sexual behavior. Females were exposed to a male with which copulation occurred in a distinctive compartment of the place preference apparatus and did not receive an incentive in the alternative compartment. After six pairings to each compartment a place preference test was conducted. Both estradiol benzoate and estradiol benzoate plus progesterone treated, ovariectomized females showed a preference for the compartment associated with sexual interaction. A second group of estradiol plus progesterone treated females was exposed to a male with which copulation occurred in one compartment of the place preference apparatus and to a sexually active, but caged, male in the other. The females tended to prefer the compartment paired with the caged male. After noncontingent intromissions, immediately preceding an additional test, the females showed a place preference for the compartment paired with sexual interaction. The presented observations indicate the potential use of the place preference procedure in studying opposing motivational processes associated with the unconditioned sequence of responses that characterize the species-specific pattern of sexual behavior.     

Loss of shoaling preference for familiar individuals in captive-reared crimson spotted rainbowfish Melanotaenia duboulayi

Captive-reared rainbowfish Melanotonia duboulayi showed no preference for familiar individuals in an experiment examining shoaling preferences. Fortnightly re-examination of the shoaling preferences of the captive-reared population showed that the lack of preference for familiar individuals did not alter over an 8 week period. The same experiment performed on laboratory-reared offspring raised in isolated groups for 8 months since hatching also showed no preference for shoals consisting of familiar individuals. In contrast, trials performed on a wild population of M. duboulayi found a strong preference for familiar shoalmates, a result that is consistent with previous studies. The lack of shoaling preferences in captive-reared populations is probably the result of relaxed selection and inbreeding in the captive environment. The consequences of captive breeding for fish social behaviour are discussed with particular reference to hatchery production.     

GABA(B) receptor agonist baclofen attenuates the development and expression of d-methamphetamine-induced place preference in rats

The present study investigated the effect of systemic administration of the GABA(B) receptor agonist, baclofen, on the development and expression of d-methamphetamine (d-MA)-induced place preference in male Wistar rats. Using a biased and 8-day schedule of conditioning, it was found that administration of d-MA (0.5 mg/kg, i.p.) produced significant place preference. The administration of baclofen (2.5 and 5.0 mg/kg, i.p.) 30 min prior to the exposure to d-MA attenuated the development of d-MA-induced place preference (p<0.05). In addition, when it was acutely administered 30 min prior to the testing session of an already established d-MA place preference, baclofen (1.25-5.0 mg/kg, i.p.) attenuated the expression of this conditioned response in a dose-dependent manner. These results showed that baclofen suppressed the rewarding effect produced by d-MA and may be potentially effective in the treatment of methamphetamine dependence and craving.     

Fluid consumption in lithium-treated rats: Roles of stimulus novelty and context novelty

In 5 experiments thirsty rats received an injection of lithium chloride or of saline, and their consumption of fluid was monitored at 5-min intervals for 30min. The novelty of the fluid and the novelty of the test context was varied. In Experiment 1 a novel fluid (a sucrose solution) was offered in a novel context; in Experiment 2 the fluid was novel and the context was familiar (the home cage); in Experiment 3 the fluid was familiar and the context was novel; and in Experiment 4 both fluid and context were familiar. Lithium influenced fluid consumption in those designs that included at least one novel feature (Experiments 1, 2, and 3, but not in Experiment 4). Consumption was initially enhanced (with respect to the controls) when the context was novel, but was suppressed when the fluid was novel. In Experiment 5, the flavor was over-ingested after lithium treatment when it was presented in a short (5min) test conducted in a novel place, but was rejected in a subsequent consumption in the home cages. It is argued that the effect of lithium depends on two factors: enhanced attention to salient cues that modifies the exploratory responses evoked by a novel context; rapid conditioning of an aversion when the fluid consumed is novel. Implications for the use of fluid consumption as an index of lithium-induced nausea are considered.     

Features of the behavior of the rat with hereditarily determined arterial hypertension

The behaviour of spontaneously hypertensive rats (SHR strain), rats with inherited stress induced arterial hypertension (ISIAH, a new developed strain), and of their normotensive Wistar progenitors was studied. The open-field arena and a device for measuring the total activity in the home cage were used in the behavioural studies. The SHR were much more active in the open--field and home cage tests than the Wistar and ISIAH rats. The basal locomotor activity of the ISIAH strain was lower than that of the Wistar rats, but the ISIAH strain had an index of behavioural reactivity 2.7 fold higher than the Wistar or SHR strains. These behavioural characteristics corresponded to the hypertension patterns of the strains compared. Enhanced spontaneous locomotion of the SHR rats was associated with spontaneous increase in arterial blood pressure. The ISIAH rats showed low spontaneous locomotor activity, but high behavioural and blood pressure reactivity under conditions of mild emotional stress.     

Isolation versus grouped housing in rats: Differential effects of low doses of heroin in the place preference paradigm

Male Long Evans rats were reared from weaning (21–23 days) either in isolation or in groups of four for 40 days. Animals were then individually introduced to a testing apparatus consisting of two distinct chambers. A modified place preference paradigm was used consisting of 3 phases: (1) An habituation phase (4 days) during which rats were allowed free access to the entire test apparatus for 15 min. periods daily; (2) A conditioning phase (4 days) during which rats were confined to their non-preferred side for 15 minutes each day immediately following subcutaneous injection of 0, 20, 40 and 80 μg/kg of heroin HCl; (3) A test phase (1 day) during which rats were again allowed free access to the testing chamber following injection of vehicle. The difference in time spent on the conditioned side during habituation and test periods was determined. The group-reared rats showed similar effects for all doses of heroin whereas the same magnitude of drug effect was attained only at the highest dose used in the isolated rats. This differential sensitivity to heroin in the place preference paradigm is discussed in terms of the modification of behavioral effects of opiates by environmental influences.     

Spontaneous and conditioned behavior of Wistar and Long Evans rats

Spontaneous behavior (locomotion, feeding, drinking, and exploration in a two box apparatus) as well as conditioned behavior (passive and active avoidance responding, and freezing in the light-dark box apparatus) were studied in naive male Wistar and Long Evans rats. Concerning spontaneous behavior, Long Evans rats were more active during both light and dark periods, and showed better exploratory performance than Wistar rats. Concerning conditioned behavior, Long Evans rats acquired and retained better active and passive avoidance responses, and exhibited longer initial freezing than Wistar rats in the range of 0.6-1.4 mA footshocks. The results better define the important behavioral differences existing between the two strains, Long Evans rats showing consistently a higher level of alertness and a better conditioned performance.     

Various resistance of motor preference in rats exposed to forced retraining

Adult Wistar rats were trained to get food from a narrow tube under conditions of free choice of a limb. After reaching a stable level of using the preferred limb, rats (n = 35) were forced to relearn the acquired skill for reaching food with a unpreferred paw. When afterwards the rats returned to the initial conditions of free choice of a limb, 12 animals (34%) did not recover their initial preference, 8 rats (23%) were ambidextrous, and 15 animals (43%) returned to the originally preferred paw. The results demonstrated different resistance of the initial limb preference to forced retraining in different animals. It is suggested that the process of retraining per se is not the only and sufficient condition of the change in "handedness". It also suggested that the different resistance of initial preference to forced retraining reflects individual differences in a degree (intensity) of this preference, which are predetermined by internal, probably by genetic factors.     

Sexual conflict situation in the rat--model of emotional stress

It has been shown on female Wistar rats, that as a result of three months sexual deprivation, in a cage of special construction, they may develop an emotional stress leading to a change in mobility and to a discordance in the functional system maintaining the optimal level of sexual hormones in their organism. A design has been presented of a cage for creating a sexual conflict situation, which is a new model of emotional stress.     

Variation among juvenile capuchins in social influences on exploration

The exploratory or feeding activities of others might influence the timing, the place, or both, of exploratory activities among young group-living individuals, and this influence might affect the information gained by individuals during exploration. This study examined the temporal and spatial aspects of adults' influence on the exploratory behavior of juvenile capuchins, and on the juveniles' acquisition of a novel behavior. Two experimental apparatus, which were initially novel to the juvenile subjects but familiar to the adults, and which provided food when a tool was used properly, were presented to group-housed capuchin monkeys. The apparatus were presented (a) in a central area, in which all animals could interact with the apparatus and in which several older group members regularly solved the tasks (group site), and (b) in a protected site within the home cage (crèche) that only juveniles could enter, but from which the rest of the cage, including the group site, could be viewed. Juveniles contacted the apparatus at the crèche more often when there was no apparatus at the group site, but only half the individuals made greater use of the apparatus at the group site than at the crèche when an apparatus was present at both sites. Seven of nine used an apparatus more often when adults also had an apparatus, than when adults did not have an apparatus. These results indicate that juveniles' exploratory activity is only weakly related to adults' activity. The linkage appears closer for younger juveniles (20 months or less) than for older juveniles. Moreover, as only older juveniles learned to solve the tasks, coordination of exploration with adults was evidently not related to learning a new skill. © Wiley-Liss, Inc.     

Non-exclusive spatial preference in the laying hen

Two experiments were performed to elucidate aspects of the spatial preference of domestic hens kept in battery cages.In the first experiment, 12 hens were given a choice between four cages differing in size and shape. The measure of preference used was the amount of time spent in each cage under free-access conditions. The results show that the hens spent most time in the cage with the largest floor area, but that substantial amounts of time were spent in the remaining three cages. Eight possible explanations for this non-exclusive choice are proposed: variation among hens; change of preference with time; mis-identification; constraints on decision-making; pacing; sampling; monitoring; genuine preference. The first six hypotheses are discussed with respect to this experiment.The second experiment, using 6 hens under similar conditions, was designed to distinguish between the latter two hypotheses. The results suggest there may be a monitoring component to the hens' behaviour in this apparatus, characterised by cage visits of short duration. In addition, the hens may continue to visit small cages in order to perform particular behaviour patterns. Nest-building behaviour is mentioned as one possibility.     

Towards an objective method of assessing welfare in domestic fowl

Some of the criteria which have been used for assessing the welfare of farm animals are briefly reviewed. A relatively new method employing techniques of animal learning is discussed. A prerequisite for this is knowledge of the preferences of the animals themselves for different environments. The measure of preference used in the present study was how quickly hens moved from a starting box into a given environment. Experimental data are presented which show that battery-kept hens move more quickly into a battery cage than into an open run in the garden. For both these environments, the presence of other birds increased their preference for the hens. In a second experiment, the previous experience of the birds was shown to be crucial: although battery-kept birds again moved more quickly into a cage, hens used to living outside moved more quickly into a hen run. When hens were familiar with both environments, they showed no significant preference for one environment over the other.