Studies on wild house mice VI: Differential effects of the Y chromosome on intermale aggression

The aim of this study is to determine the effects of different parts of the Y chromosome of wild house mice on aggression. To reach this goal, intercrosses were made between two selection lines for attack latency (SAL and LAL) and their congenic strains (SAL. LY and LAL. SY). This procedure resulted in F₁ hybrids that carried the same autosomes, but differed in their X chromosome and the two different parts of their Y chromosomes, the different parts of the Y chromosome being a recombining part called the pseudoautosomal region (PAR) and a non-recombining part (non-PAR). We conclude that both parts of the Y chromosome contribute slightly but significantly to variation in aggression. The major effect is accomplished by the PAR of the aggressive parent; a mirror effect is achieved by the non-PAR of the aggressive parent in interaction with the PAR. © 1994 Wiley-Liss, Inc.     

Antipredator behavior of Swiss-Webster mice in a visible burrow system

Swiss-Webster mice living in a visible burrow system (VBS) reacted to presentation of a live cat in the surface area of the VBS by retreat to the burrows and reductions in nondefensive behaviors such as eating and drinking. Live eat-exposed subjects remained in the burrows 14 hr or more, while subjects exposed to a toy (plush) cat prior to live cat exposure reemerged almost immediately and made many contacts with the toy cat. However, subjects exposed first to the cat and later to a toy cat showed intermediate surface reemergence times and cat contacts during toy cat tests, indicating strong sensitization effects of prior live cat exposure. Previous studies indicated that rats in this situation show retreat to the burrows, surface avoidance, and reduction in nondefensive behaviors. The mouse pattern was similar, with the notable exception that in the first 5min block after cat presentation, mice rapidly alternated retreat to the burrow chambers with reappearance in the tunnel segment near the surface, to scan the surface visually and sniff. Movement during this time block involved a stretch attend posture characteristic also of risk assessment activities in rats. Such visual and olfactory inspection of the cat is not seen in rats in the VBS. This difference may be related to the finding that rats, but not mice, emit ultrasonic “alarm cries” during and after cat exposure. © 1995 Wiley-Liss, Inc.     

Analysis of the targets and tactics of conspecific attack and predatory attack in northern grasshopper mice onychomys leucogaster

Comparisons of tactics of fighting between species are often difficult to make since the body targets attacked may differ. Thus it becomes difficult to assess whether differences in fighting tactics are due to species-specific differences in the tactics themselves or due to the different targets attacked. A solution to this problem is to analyse the tactics of a species that attacks different targets under different circumstances. In this way, differences in tactics can be more readily attributed to differences in targets. In this study, resident male northern grasshopper mice (Onychomys leucogaster) were tested against intruding male conspecifics and against laboratory mice (Mus musculus domesticus). Conspecifics were mainly bitten on the lower dorsum, whereas prey were bitten and killed by bites to the nape of the neck. Therefore, it was possible to analyze the tactics of attack by grasshopper mice when attacking different body targets. For example, in order to defend the lower dorsum and the nape, both intruding conspecifics and prey adopted an upright defensive posture. Resident grasshopper mice used the lateral attack tactic to gain access to the lower flanks but not the nape. This illustrates that the lateral attack tactic is not merely a tactic suitable for overcoming the upright defense tactic, but is used in this context only when the target attacked is on the opponent's posterior dorsum. Such withinpecies comparison enables the identification of the contextual rules which govern the use of fighting tactics. © 1992 Wiley-Liss, Inc.     

血糖水平对STZ鼠探究行为及学习记忆的影响

为了解不同血糖水平下链脲佐菌素诱导鼠（STZ鼠）探究行为与学习和记忆的变化情况,把60只STZ鼠按血糖水平分成高血糖组、良好血糖组和低血糖组3组,进行延迟时间、探究时间测定和小鼠跳台试验,并与正常对照组比较。结果发现,良好血糖组与正常对照组各检测指标均相近;3组STZ鼠延迟时间、完成迷津作业时间均按血糖值递增;组间差异显著;小鼠跳台试验中高血糖组的错误数最多,24小时后错误数最少,前后差值有组间差异;延迟时间、探究时间与血糖呈显著正相关,错误数差值与血糖呈显著负相关。结果表明,高血糖鼠的探究行为和学习能力最差,但对被动回避学习的记忆保持相对较好。     

An olfactory discrimination procedure for mice

This paper describes an olfactory discrimination procedure for mice that is inexpensively implemented and leads to rapid discrimination learning. Mice were first trained to dig in small containers of sand to retrieve bits of buried chocolate. For discrimination training, two containers were presented simultaneously for eight trials per session. One container held sand mixed with cinnamon, and the other held sand mixed with nutmeg. Both containers were baited with chocolate buried in the sand. One odor was designated S+, and mice were allowed to dig and retrieve the chocolate from this container. The other odor was S-, and both containers were removed immediately if subjects began to dig in an S- container. After meeting a two-session acquisition criterion, subjects were given a series of discrimination reversals. In Experiment 1, 12 Swiss-Webster mice (6 male and 6 female) acquired the olfactory discrimination in three to five sessions and completed 3 to 10 successive discrimination reversals within a 50-session testing limit. In Experiment 2, subjects were 14 Pah(enu2) mice, the mouse mutant for phenylketonuria; 7 were homozygotes in which the disorder was expressed (PKU), and 7 were heterozygotes with normal metabolism (non-PKU). Thirteen mice completed pretraining in four to seven sessions, acquisition required 3 to 12 sessions, and all mice completed at least three reversals. Learning rates were similar in PKU and non-PKU mice. We discuss issues related to implementation and several potentially useful procedural variations.     

Mice selectively bred for an open field activity increase after maze learning

A unidirectional selective breeding experiment performed over six generations resulted in a line of mice (S6), which differed from the maintained unselected Swiss albino strain, called normal (N) strain, in the following respects: S6 mice increased their open field activity after maze learning significantly more than N mice. S6 mice ambulated more and exhibited more thigmotactic behaviour in a circular open field than N mice. S6 mice were superior than N mice in regard to maze learning capacity. Finally, S6 mice were interpreted as significantly less emotional according to their defecation, more responsive to novelty according to their urine pattern and more aggressive than N mice.     

Antiaggressive Effects of Zolpidem and Zopiclone in Agonistic Encounters Between Male Mice

The effects of benzodiazepines on various types of aggression have been extensively studied. These substances produce their pharmacological effects by allosterically modulating the action of GABA via specific recognition sites on the GABA_A receptor called omega 1 and omega 2. The antiaggressive profile of non‐benzodiazepine compounds that also act at omega sites, such as zopiclone (a non‐selective omega 1 and 2 ligand) and zolpidem (a selective omega 1 ligand) has been scarcely explored. In this study, we examined the action of zolpidem (0.75‐3 mg/kg, intraperitoneally) and zopiclone (1.5‐6 mg/kg), administered acutely or subchronically for 10 days, on agonistic behavior elicited by isolation in male mice. Individually housed mice were exposed to anosmic “standard opponents” 30 min after drug administration, and the encounters were videotaped and evaluated using an ethologically based analysis. Acute treatment with zopiclone produced a marked antiaggressive effect, reducing offensive behaviors (threat and attack) at all doses used (1.5, 3, and 6 mg/kg) without affecting immobility. Likewise, the intermediate dose of zolpidem (1.5 mg/kg) significantly decreased aggression in a specific manner, without altering immobility, whereas the highest dose (3 mg/kg) provoked a reduction of aggression accompanied by a weak (but significant) increase of immobility. With repeated treatment, no tolerance to the antiaggressive effects of zopiclone and zolpidem was developed. It is concluded that omega sites at the GABA_A receptor could be involved in the control of aggression. Aggr. Behav. 28:416–425, 2002. © 2002 Wiley‐Liss, Inc.     

The GABAergic effect of low doses of lorazepam on social behavior

The aim of this work was to test the antiaggressive effects of lorazepam and to determine whether these effects were mediated by benzodiazepine receptors. In a first experiment, male mice were injected with lorazepam in a range of low doses (0.05, 0.1, 0.2, and 0.6 mg/kg) or saline solution. In a second experiment, 1 mg/kg of Ro 15‐1788, a benzodiazepine receptor antagonist, and a saline solution were injected before the behavioral test. Results showed that 0.6 mg/kg of lorazepam was the only dose that decreased the total duration of threat (P < .01) and social investigation (P < .05) and that 1 mg/kg of Ro 15‐1788 had no effects. In the third experiment, animals received two injections: 0.6 mg/kg of lorazepam plus 1 mg/kg of Ro 15‐1788, 0.6 mg/kg of lorazepam plus saline solution, or saline solution plus saline solution. Those treated with lorazepam and saline solution spent less time digging (P < .001), threatening (P < .001), and attacking (P < .05) and more time avoiding the opponent (P < .01) or being immobile (P < .001) than the controls. Ro 15‐1788 was successful in completely antagonizing the behavior modulated by lorazepam. Aggr. Behav. 28:248–256, 2002. © 2002 Wiley‐Liss, Inc.     

Differential sensitivity to the effects of nicotine and bupropion in adolescent and adult male OF1 mice during social interaction tests

Few studies have compared the action of both nicotine (NIC) and bupropion (BUP), an antidepressant used to treat NIC dependence, on social and aggressive behavior at different ages. This study aims to determine whether these drugs produce differential effects in adolescent (postnatal day: 36-37) and adult (postnatal day: 65-66) mice that have been housed individually for 2 weeks in order to induce aggressive behavior. Mice received BUP (40, 20, or 10 mg/kg), NIC (1, 0.5, and 0.25 mg/kg as base), or vehicle earlier to a social interaction test. BUP (40 mg/kg) decreased social investigation and increased nonsocial exploration in both adolescent and adult mice. The same effects were also observed in adult mice administered with a lower dose of the same drug (20 mg/kg). In adolescents, NIC (1 mg/kg) decreased social investigation, but this effect did not reach statistical significance in adults. In conclusion, a differential sensitivity to the effects of NIC or BUP emerged in some of the behavioral categories when the two age groups were compared.     

Effects of MK-801 and ethanol combinations on memory consolidation in CD1 mice: involvement of GABAergic mechanisms

In the present research the effect of the noncompetitive N-methyl-d-aspartate receptor antagonist MK-801 and ethanol combinations on memory consolidation and the involvement of GABAergic mechanisms in this effect were investigated in CD1 mice injected intraperitoneally with the drugs immediately or 120 min after training in a one-trial inhibitory avoidance apparatus and tested for retention 24 h later. The results showed that (a) the retention performances of mice were impaired in a dose-dependent manner by immediate posttraining MK-801 (0.2 and 0.3, but not 0.1 mg/kg) and ethanol (1 and 2, but not 0.5 g/kg) administrations; (b) an otherwise ineffective dose of MK-801 (0.1 mg/kg) enhanced the deleterious effect exerted by ethanol (1 and 2 g/kg); (c) an otherwise ineffective dose of muscimol (0.5 mg/kg) enhanced, while otherwise ineffective doses of picrotoxin (0.25 mg/kg) or bicuculline (0.1 mg/kg) antagonized, this effect; and (d) no effect was observed when the treatments were carried out 120 min after training, suggesting that the effects observed following immediate posttraining administrations were due to the influence on the consolidation of memory. From these experiments it is evident that (a) MK-801 enhances ethanol's effects on memory consolidation and (b) GABAergic mechanisms are involved in this effect.