Sequences of feeding,sampling and exploration by wild and laboratory rats

Adult male wild rats and male laboratory rats, all Rattus norvegicus, were kept alone for 11 d is a residential maze. The maze had a central nest box and four arms radiating from it. Movement in the arms was automatically recorded. Three foods were supplied, one at the end of each of three arms; the fourth arm was empty. One food was usually much preferred to the othe two. Except on Days 1—3, access to the arms was for only 3h daily.The rate of visiting the arms declined during the first 3 d. The wild rats were more ‘active’ than the domestic in that they made more visits; but they spent less time in the arms. Visits were of two kinds: (a) short, usually < 1min; (b) long (> 4 min.: meals). The wild rats had shorter meals than the donestic.A 3-h period of access usually began with a bout of short visits to the arms. Each long visit to a food arm (a meal) was also typically followed by such a bout, sometimes after a period in the nest box (drinking). the first short visit after a meal by a wild rat was most often to the empty arm; but domestic rats distributed these visits evenly among the three arms in which they had not been feeding. In a given bout the second short visit by a wild rat, but not a domestic, tended to repeat the first.We interpret a bout of short visits as a patrol or re-exploration of the living space which may include sampling of all accessible foods. When a bout occured at the beginning of access to the maze arms, exploring was in ‘competition’ with eating; a bout after a meal may have represented ‘disinhibition’ of exploring.     

Toxoplasma infection and response to novelty in mice

Three groups of mice were infected with Toxoplasma and used for behavioral testing using a Y-maze. One group was infected when adult and two groups congenitally, one of these born to dams infected during gestation, the other to dams chronically infected prior to mating. In an initial habituation period each mouse was exposed to a black arm and stem of the maze, entrance to a white arm being blocked by a transparent door. In a subsequent free-choice trial both arms were black and the mouse was free to explore all parts of the maze. During both periods infected mice were more active than controls. Infected mice engaged in less grooming behavior indicative of less approach-avoidance conflict than controls prior to entry into a choice arm at the beginning of the free-choice trial. Infected mice spent more time in the familiar than in the novel (previously blocked) arm during the free-choice trial; conversely, uninfected mice spent more time in the novel than in the familiar arm. It is suggested that the reported behavioural changes would lead to dissemination of the infection in the environment by ultimately making infected mouse intermediate hosts more susceptible to predation by domestic cats, the definitive hosts of Toxoplasma.     

Rapid Learning of Magnetic Compass Direction by C57BL/6 Mice in a 4-Armed ‘Plus’ Water Maze

Magnetoreception has been demonstrated in all five vertebrate classes. In rodents, nest building experiments have shown the use of magnetic cues by two families of molerats, Siberian hamsters and C57BL/6 mice. However, assays widely used to study rodent spatial cognition (e.g. water maze, radial arm maze) have failed to provide evidence for the use of magnetic cues. Here we show that C57BL/6 mice can learn the magnetic direction of a submerged platform in a 4-armed (plus) water maze. Naïve mice were given two brief training trials. In each trial, a mouse was confined to one arm of the maze with the submerged platform at the outer end in a predetermined alignment relative to magnetic north. Between trials, the training arm and magnetic field were rotated by 180^° so that the mouse had to swim in the same magnetic direction to reach the submerged platform. The directional preference of each mouse was tested once in one of four magnetic field alignments by releasing it at the center of the maze with access to all four arms. Equal numbers of responses were obtained from mice tested in the four symmetrical magnetic field alignments. Findings show that two training trials are sufficient for mice to learn the magnetic direction of the submerged platform in a plus water maze. The success of these experiments may be explained by: (1) absence of alternative directional cues (2), rotation of magnetic field alignment, and (3) electromagnetic shielding to minimize radio frequency interference that has been shown to interfere with magnetic compass orientation of birds. These findings confirm that mice have a well-developed magnetic compass, and give further impetus to the question of whether epigeic rodents (e.g., mice and rats) have a photoreceptor-based magnetic compass similar to that found in amphibians and migratory birds.     

Naltrexone potentiates both amnestic and anxiolytic effects of chlordiazepoxide in mice

Studies have suggested that opioid antagonists potentiate the anxiolytic effect but not the amnestic action of chlordiazepoxide (CDZ). We investigated the effects of naltrexone (NAL) on the anxiolytic and amnestic effects of CDZ in mice tested in the plus-maze discriminative avoidance task (DAT). Mice are conditioned to choose between two enclosed arms (one of which aversive) while avoiding the two open arms of the apparatus. This task measures memory (time spent in the aversive vs. time in the non-aversive enclosed arms) and anxiety (time spent in the open arms). Mice treated with saline (SAL) or 5 mg/kg NAL, and SAL or 2.5 mg/kg CDZ were submitted to DAT training. The test was performed 24 h later, without aversive stimuli. In the training, NAL + CDZ group showed higher percent time spent in the open arms than all the other groups. In the test, NAL + CDZ (but not SAL + CDZ) group showed higher percent time spent in the aversive enclosed arm than SAL + SAL and NAL + SAL groups. The data suggest that NAL potentiates the small decreases in anxiety and retention induced by a subeffective dose of CDZ.     

小鼠动物实验方法系列专题(五) 应用高架十字迷宫分析小鼠焦虑行为

高架十字迷宫(the elevated plus maze,EPM)是研究小鼠焦虑行为的重要实验,本文介绍了EPM的原理和实验步骤。将小鼠置于开臂闭臂接合处,面向开臂,通过录像记录分析小鼠在EPM的表现。结果发现,两种小鼠均可成功完成实验,C57小鼠在EPM内较不活跃,闭臂滞留时间占总时间百分比显著高于129Sv小鼠。应用EPM可以简单直观地分析小鼠焦虑行为。     

Elevated Plus Maze for Mice

Although the mouse genome is now completely sequenced, the functions of most of the genes expressed in the brain are not known. The influence of a given gene on a specific behavior can be determined by behavioral analysis of mutant mice. If a target gene is expressed in the brain, behavioral phenotype of the mutant mice could elucidate the genetic mechanism of normal behaviors. The elevated plus maze test is one of the most widely used tests for measuring anxiety-like behavior. The test is based on the natural aversion of mice for open and elevated areas, as well as on their natural spontaneous exploratory behavior in novel environments. The apparatus consists of open arms and closed arms, crossed in the middle perpendicularly to each other, and a center area. Mice are given access to all of the arms and are allowed to move freely between them. The number of entries into the open arms and the time spent in the open arms are used as indices of open space-induced anxiety in mice. Unfortunately, the procedural differences that exist between laboratories make it difficult to duplicate and compare results among laboratories. Here, we present a detailed movie demonstrating our protocol for the elevated plus maze test. In our laboratory, we have assessed more than 90 strains of mutant mice using the protocol shown in the movie. These data will be disclosed as a part of a public database that we are now constructing. Visualization of the protocol will promote better understanding of the details of the entire experimental procedure, allowing for standardization of the protocols used in different laboratories and comparisons of the behavioral phenotypes of various strains of mutant mice assessed using this test.     

非繁殖期大仓鼠对同种气味的反应和个体间的行为关系

在实验室通过对陌生成年大仓鼠（Ｃｒｉｃｅｔｕｌｕｓｔｒｉｔｏｎ）非繁殖期的气味偏好,性别选择和两鼠间的行为关系的实验研究表明,用Ｙ－型迷宫进行选择测试时,与空白组比较,大仓鼠了同种个体鼠垫的气味,在雌雄巢垫气味之间,雌鼠偏好雄性巢垫的气味,雄鼠不表现性别偏好,与空白组比较,被试鼠选择同种个体;在雌雄个体之间,雄性大仓鼠选择同性个体,雌性不表现性别偏好,在观察箱内,无论同性相遇还是异性相遇,两鼠间攻     

The use of the elevated plus maze as an assay of anxiety-related behavior in rodents

The elevated plus maze is a widely used behavioral assay for rodents and it has been validated to assess the anti-anxiety effects of pharmacological agents and steroid hormones, and to define brain regions and mechanisms underlying anxiety-related behavior. Briefly, rats or mice are placed at the junction of the four arms of the maze, facing an open arm, and entries/duration in each arm are recorded by a video-tracking system and observer simultaneously for 5 min. Other ethological parameters (i.e., rears, head dips and stretched-attend postures) can also be observed. An increase in open arm activity (duration and/or entries) reflects anti-anxiety behavior. In our laboratory, rats or mice are exposed to the plus maze on one occasion; thus, results can be obtained in 5 min per rodent.     

Two-day radial-arm water maze learning and memory task; robust resolution of amyloid-related memory deficits in transgenic mice

The radial arm water maze (RAWM) contains six swim paths (arms) extending out of an open central area, with an escape platform located at the end of one arm (the goal arm). The goal arm location remains constant for a given mouse. On day 1, mice are trained for 15 trials (spaced over 3 h), with trials alternating between visible and hidden platform. On day 2, mice are trained for 15 trials with the hidden platform. Entry into an incorrect arm is scored as an error. The RAWM has the spatial complexity and performance measurement simplicity of the dry radial arm maze combined with the rapid learning and strong motivation observed in the Morris water maze without requiring foot shock or food deprivation as motivating factors. With two sessions each day, 16 mice can be tested over 2 days.     

Social status, activity and preputial glands of wild and domestic house mice

Scent marking by deposition of urine, and the preputial glands, of adult, male, wild house mice, Mus mmmlus L., were studied and compared with those of an outbred domestic strain. The preputial glands of dominant wild mice were always heavier than those of subordinates. No dominance relationships could be established among the domestic mice. For study of scent marking each mouse was observed singly in a residential maze. Dominant wild mice marked more than the subordinates. The domestic mice scent-marked much less even than the subordinate wild mice. Subordinate wild mice spent less time than the dominant wild mice outside the nest; but the number of excursions outside the nest made by the subordinates resembled that of the dominants. Hence social status influenced the pattern of movements in a structured environment.     

The potential of an insect pheromone lure,Z‐7‐dodecen‐1‐yl acetate,compared with peanut butter to attract laboratory and wild rats and mice

Abstract

We compared the attractiveness to rats and mice of two lures, the pheromone Z‐7‐dodecen‐1 ‐y 1 acetate and peanut butter. In the first part of the study, laboratory‐bred rats and mice were placed in a Y‐maze. Each arm of the maze offered their normal food, plus either the pheromone or 5% ethanol as a control. There were no significant differences, by species or sex, in the number of visits or the amount of time spent in each arm. The male mice took significantly less time, however, to enter the control arm of the maze than the pheromone arm. In addition, female mice were less active during the first 5 min of the Y‐maze study than during the 5 min familiarisation period, suggesting a repellent effect of the pheromone lure. In the second part of the study, tracking tunnels were placed out in the field and baited with one of three lures—the pheromone, peanut butter or a 5% ethanol control. There was no significant difference in the number of visits by mice to tunnels containing the three lures, but rats made more visits to the tunnels containing peanut butter in the “Test” stage than in the “Neo” stage. The wild rats and mice were found not to be neophobic, suggesting the standard 3‐week familiarisation period is not necessary.     

Recognition of burrow's olfactory signature in blue petrels, Halobaena caerulea: an efficient discrimination mechanism in the dark

Previous work has shown that blue petrels need olfaction to home. We investigated whether they also recognize an olfactory signature of their own nest. We performed T-maze experiments in which maze arms were connected with the subject bird's burrow and with the burrow of a conspecific neighbour. Of 23 birds, 16 were able to recognize the arm leading to their own burrow. In a second experiment, we positioned the maze in front of the subject's burrow but the maze arms were closed and did not enter the burrow. Consequently, no burrow odours could be sensed by the bird. In this case, 85% of birds (17 of 20) failed to choose, suggesting that petrels were not motivated to choose by positional cues in the absence of odour cues. We explored this idea further by performing a homing experiment whereby homing birds had to relocate an artificially displaced burrow entrance. Blue petrels homed, ignoring the natural burrow entrance and using the new artificial one. The ability to smell their own burrow allows blue petrels to return to the colony at night and to find the correct nest.     

Effects of acute and chronic nicotine on elevated plus maze in mice: involvement of calcium channels

The current experiments examined the anxiety-related effects of acute and repeated nicotine administration using the elevated plus maze test in mice. Nicotine (0.1 mg/kg s.c., 5 and 30 min after injection; 0.5 mg/kg, s.c., 5 min after injection) had an anxiogenic effect, shown by specific decreases in the percentage of time spent on the open arms and in the percentage of open arm entries. Tolerance developed to this anxiogenic action after 6 days of daily nicotine administration (0.1 mg/kg, s.c.). Five minutes after the seventh injection, an anxiolytic effect was observed, i.e., specific increases in the percentage of time spent on the open arms and in the percentage of open arm entries. L-type voltage-dependent calcium channel antagonists nimodipine (5 and 10 mg/kg, i.p.), flunarizine (5 and 10 mg/kg, i.p.), verapamil (5, 10, 20 mg/kg) and diltiazem (5, 10, 20 mg/kg, i.p.) were also injected prior to an acute low dose of nicotine or to each injection of chronic nicotine. Our results revealed that calcium channel blockers dose-dependently attenuated both an anxiogenic effect of nicotine as well as the development of tolerance to this effect. Our results suggest that neural calcium-dependent mechanisms are involved in the anxiety-related responses to acute and chronic nicotine injection that may ultimately lead to addiction and smoking relapse in human smokers.     

Possible involvement of nitric oxide in chlordiazepoxide-induced anxiolysis in mice.

Mice challenged with the anxiolytic benzodiazepine chlordiazepoxide exhibited significant increases in the percent of total entries into and percent of total time spent on open arms of an elevated plus maze. Systemic pretreatment with the nitric oxide synthase-inhibitor L-NG-nitro arginine (L-NOARG) antagonized these effects of chlordiazepoxide. This inhibitory effect of L-NOARG was stereospecifically and completely reversed by intracerebroventricular administration of L-arginine but not D-arginine. These findings suggest a possible role of nitric oxide in the anxiolytic effect of chlordiazepoxide in the elevated plus maze.     

Differences in anxiety-related behavior between apolipoprotein E-deficient C57BL/6 and wild type C57BL/6 mice

The influence of ApoE gene deletion on the anxiety state has not been previously investigated. The elevated plus maze was used in this study to determine differences in anxiety-related behavior between apoE-deficient and wild type C57BL/6 mice. The apoE-deficient mice demonstrated less anxiety on the elevated plus maze by spending more time in the open arms of the elevated plus maze compared to wild type mice (p<0.001). Additionally, female apoE-deficient mice visited the open arm of the maze more often than their apoE-deficient male counterpart (p<0.05). The anxiety state and/or sex are possible variables to be considered when designing physiological and/or behavioral studies involving mice that are apoE-deficient.     

Anxiolytic activity of Indian Hypericum perforatum Linn: an experimental study

The putative anxiolytic activity of 50% ethanolic extract of Indian Hypericum perforatum (IHp) was investigated in rats using various experimental paradigms of anxiety viz. open field exploratory behaviour (OFB), elevated plus maze (EPM), elevated zero maze (EZM), novelty induced suppressed feeding latency (FL) and social interaction (SI) tests. Pilot studies indicated that single dose administration of IHp had little to no acute behavioural effects, hence the extract of IHp was administered orally at different dose levels once daily for three consecutive days, while lorazepam (LR) (0.5 mg/kg, i.p.) was administered acutely. IHp extract (100 and 200 mg/kg, p.o.) showed significant anxiolytic effects on all the paradigms of anxiety. The results indicate that IHp and LR induced a significant increase in open field ambulation and slight increase in rearings and activity in centre, whereas grooming and fecal droppings remain unchanged. In EPM, significant augmentation of open arm entries, open arm/closed arm entries ratio and time spent on open arms was noted in IHp treated rats. In EZM test, significant increase in time spent on open arms and entries in open arms were observed, whereas slight increase in head dips and stretched attend postures were also observed. IHp and LR significantly attenuated the novelty induced increase in feeding latency. IHp treated rats also showed significant increase in social interaction in the novel environment. The IHp extracts showed consistent and significant anxiolytic activity in all the tests. The effects induced by 50% ethanolic extract of IHp were less marked than those of lorazepam were.     

Effects of (−)-Sesamin on Chronic Stress-Induced Anxiety Disorders in Mice

This study investigated the effects of (?)-sesamin on chronic electric footshock (EF) stress-induced anxiety disorders in mice. Mice were treated with (?)-sesamin (25 and 50 mg/kg) orally once a day for 21 days prior to exposure to EF stress (0.6 mA, 1 s every 5 s, 3 min). Mice treated with (?)-sesamin (25 and 50 mg/kg) exhibited less severe decreases in the number of open arm entries and time spent on open arms in the elevated plus-maze test and the distance traveled in the open field test following exposure to chronic EF stress. Similarly, mice treated with (?)-sesamin exhibited significantly less severe decreases in brain levels of dopamine, norepinephrine, and serotonin following exposure to chronic EF stress. Increases in serum levels of corticosterone and expression of c-Fos were also less pronounced in mice treated with (?)-sesamin (25 and 50 mg/kg). These results suggest that (?)-sesamin may protect against the effects of chronic EF stress-induced anxiety disorders by modulating dopamine, norepinephrine, and serotonin levels, c-Fos expression, and corticosterone levels.     

Use of an Eight-arm Radial Water Maze to Assess Working and Reference Memory Following Neonatal Brain Injury

Working and reference memory are commonly assessed using the land based radial arm maze. However, this paradigm requires pretraining, food deprivation, and may introduce scent cue confounds. The eight-arm radial water maze is designed to evaluate reference and working memory performance simultaneously by requiring subjects to use extra-maze cues to locate escape platforms and remedies the limitations observed in land based radial arm maze designs. Specifically, subjects are required to avoid the arms previously used for escape during each testing day (working memory) as well as avoid the fixed arms, which never contain escape platforms (reference memory). Re-entries into arms that have already been used for escape during a testing session (and thus the escape platform has been removed) and re-entries into reference memory arms are indicative of working memory deficits. Alternatively, first entries into reference memory arms are indicative of reference memory deficits. We used this maze to compare performance of rats with neonatal brain injury and sham controls following induction of hypoxia-ischemia and show significant deficits in both working and reference memory after eleven days of testing. This protocol could be easily modified to examine many other models of learning impairment.     

The type 1 equilibrative nucleoside transporter regulates anxiety-like behavior in mice

Activation of adenosine receptors in the brain reduces anxiety-like behavior in animals and humans. Because nucleoside transporters regulate adenosine levels, we used mice lacking the type 1 equilibrative nucleoside transporter (ENT1) to investigate whether ENT1 contributes to anxiety-like behavior. The ENT1 null mice spent more time in the center of an open field compared with wild-type littermates. In the elevated plus maze, ENT1 null mice entered more frequently into and spent more time exploring the open arms. The ENT1 null mice also spent more time exploring the light side of a light-dark box compared with wild-type mice. Microinjection of an ENT1-specific antagonist, nitrobenzylthioinosine (nitrobenzylmercaptopurine riboside), into the amygdala of C57BL/6J mice reduced anxiety-like behavior in the open field and elevated plus maze. These findings show that amygdala ENT1 modulates anxiety-like behavior. The ENT1 may be a drug target for the treatment of anxiety disorders.     

Testing for episodic-like memory in rats in the absence of time of day cues: replication of Babb and Crystal

Two experiments were performed to look for evidence of episodic-like memory in rats. On each of a series of trials on an eight-arm radial maze, rats in two groups entered four open arms in Phase 1, with reward pellets on three arms and a favored reward (chocolate in Experiment 1 and cheese in Experiment 2) on the remaining arm. Phase 2 retention tests were given 30 min or 4 h after Phase 1, with all eight arms open. The four arms not entered in Phase 1 all contained reward pellets, and the three arms that contained pellets in Phase 1 were empty. In the replenish short group, the favored reward was replenished at the same location where it was found in Phase 1 at the 30 min retention interval but was absent (Experiment 1) or degraded (Experiment 2) at the 4 h retention interval. In the replenish long group, the favored reward was replenished at the 4 h retention interval but not at the 30 min retention interval. Over a number of daily trials that randomly mixed short and long delays, rats in both experiments learned to return earlier to the arm containing the favored reward at the retention interval when it was replenished than at the retention interval when it was absent or degraded. These results replicate earlier findings [Babb, S.J., Crystal, J.D., 2005, Discrimination of what, when, and where: implications for episodic-like memory in rats. Learn. Mot., 36, 177-189] and provide evidence of episodic-like memory in rats.