Sexual Behavior of C57BL/10 Mice and its Relation to Early Social Experience

Unexpectedly, imitation of value judgments (design preferences) by male and female third and sixth graders (N = 366) generally did not result from exposure to adult film models (Ms). As expected, the variable of identification was more sensitive to the experimental manipulation of M's characterological traits than the measure of imitation. As expected, children identified with an honest as opposed to dishonest M; however, dominance versus submission had no such effect, suggesting that power related theories are far from adequate in explaining identification. In third grade, children viewed leadership strictly in terms of dominance, while, unexpectedly, in sixth they viewed leadership in terms of character (honesty). Other unexpected significant results also were heuristic, suggesting that several dependent variables not previously emphasized in the experimental modeling literature with children merit greater attention: negative imitation (negativism), negative identification (disaffiliation), and the effects of characterological and physical appearance variables on both identification and imitation.     

Visual snake aversion in Octodon degus and C57BL/6 mice

Animal Cognition - Phobia against spiders or snakes is common in humans, and similar phobia-like behaviors have been observed in non-human animals. Visual images of snakes elicit phobia in humans,...     

Varenicline ameliorates ethanol-induced deficits in learning in C57BL/6 mice

Ethanol is a frequently abused drug that impairs cognitive processes such as learning. Varenicline, an α4β2 nicotinic receptor partial agonist and α7 nicotinic receptor full agonist prescribed for smoking cessation, has been shown to decrease ethanol consumption. The current study investigated whether varenicline could ameliorate ethanol-induced deficits in learning and whether varenicline alters blood alcohol concentration in C57BL/6 mice. Conditioning consisted of two auditory conditioned stimulus (CS; 30 s, 85 dB white noise)—foot shock unconditioned stimulus (US; 2 s, 0.57 mA) pairings. For all studies, saline or ethanol (1.0, 1.5, 2.0 g/kg i.p.) was administered 15 min before training, and saline or varenicline (0.05, 0.1, 0.2 mg/kg i.p.) was administered 60 min before either training or testing. For blood alcohol analysis, saline or varenicline (0.1 mg/kg) was administered 60 min before collection, and saline or ethanol (1.0, 1.5, 2.0 g/kg) was administered 15 min before collection. Varenicline dose-dependently ameliorated ethanol-induced conditioning deficits for all three doses of ethanol when administered before training but not when administered 24 h later, before testing. In addition, varenicline did not alter blood alcohol concentration. The smoking cessation aid varenicline may have therapeutic uses for treating ethanol-associated disruptions in cognitive processes.     

Sex differences in memory for landmark arrays in C57BL/J6 mice

The most robust sex differences in cognition across polygynous mammalian species are the sex-specific patterns of the use of spatial cues during encoding and orientation. In laboratory rats, wild rodents, and humans, females orient preferentially to the features and arrangement of local landmarks, while males preferentially attend to distant landmarks. Yet this sex-specific pattern is often absent or reversed in the laboratory mouse, a species representing a major laboratory model of neural mechanisms. We explored sex differences in the C57BL/J6 strain of laboratory mouse by employing tasks that were motivated by the natural patterns of exploration. We predicted that such tasks would unmask the predicted default polygynous patterns of cue use by females and males. We used two standard tasks, a novel object recognition task and a five-stage serial object dishabituation task. On the first task, the results showed a female advantage in detecting the novel object, as predicted by prior results from other polygynous species. In the second task, we found, also as predicted, a male advantage in performance when the polarization of the array was distorted and a female advantage in performance when the local array was re-arranged. The pattern of sex-specific advantages in performance in C57BL/J6 mouse is thus concordant with that found in other polygynous mammals.     

Behaviors of Swiss-Webster and C57/BL/6N sin mice in a fear/defense test battery

When confronted by an approaching threat stimulus (experimenter or laboratory rat), Swiss-Webster mice show initial flight, followed by freezing and defensive vocalization and biting, the latter only when escape is blocked. These defense patterns resemble those of the wild rat, suggesting that mice of this strain do not show the reductions in flight and defensive threat/attack that are typical of laboratory rats. C57/BL/6N Sin strain mice showed fewer avoidances to an approaching predator, as well as reduced vocalization and defensive biting, a pattern more similar to that of laboratory rats. As with rats, female mice appeared to be more defensive to a predator. They showed greater reactivity to dorsal contact and more frequent defensive biting and jump attacks than males of the same strains. These patterns of defensive behaviors suggest that, although strain differences in defense are substantial, laboratory mice are suitable for, and may offer several advantages in, the study of the genetic, endocrine, and pharmacological basis of antipredator defense. © 1995 Wiley-Liss, Inc.     

Dopamine D2 receptors mediate reversal learning in male C57BL/6J mice

Dopamine is critical for directing goal-oriented behavior. We investigated dopamine D₂ receptor involvement in reversal learning and reinforcement efficacy in mice lacking functional dopamine D₂ receptors and their heterozygous and wild-type littermates. Mice discriminated between two odors to receive a food reinforcer: One odor signaled a reinforcer (S⁺); the other odor signaled no reinforcer (S⁻). After mice learned the S⁺/S⁻ relationship, we inverted the reinforcement contingencies. The necessary number of trials to relearn the new reinforcement contingencies served as our index of reversal learning. Mice lacking functional dopamine D₂ receptors repeatedly failed to inhibit previously reinforced responses during reversal trials. In a separate experiment, mice responded for reinforcers on a progressive ratio schedule of reinforcement. Mice lacking functional dopamine D₂ receptors earned significantly fewer reinforcers than did heterozygous mice. Our results suggest that dopamine D₂ receptors regulate reversal learning and influence the reinforcing efficacy of natural rewards.     

Adult but not aged C57BL/6 male mice are capable of using geometry for orientation

Geometry, e.g., the shape of the environment, can be used by numerous animal species to orientate, but data concerning the mouse are lacking. We addressed the question of whether mice are capable of using geometry for navigating. To test whether aging could affect searching strategies, we compared adult (3- to 5-mo old) and aged (20- to 21-mo old) C57BL/6 male mice. We established a water maze task in which spatial information is provided by one landmark proximal to the target (featural information) and by the rectangular shape of the maze (geometric information). By means of probe trials in which we manipulated the presence of these two kinds of information, we show that adult mice can use both geometry and landmark to orientate. By contrast, aged mice do not use geometry and rely exclusively on the landmark to locate the platform. This study provides the first evidence that mice are capable of using geometric information for orientation and that this ability declines in aged animals.     

Nicotine enhances contextual fear conditioning in C57BL/6J mice at 1 and 7 days post-training

Nicotine has been demonstrated to enhance learning processes. The present experiments extend these results to examine the effects of nicotine on acquisition and consolidation of contextual and cued fear conditioning, and the duration of nicotine's enhancement of conditioned fear. C57BL/6 mice were trained with two pairings of an auditory CS and a foot shock US. Multiple doses of nicotine were given before or immediately after training and on testing day (0.0, 0.050, 0.125, 0.250, and 0.375 mg/kg, i.p). Freezing to both the context and auditory CS was measured 24h after training and again 1 week after training. Mice did not receive nicotine for the 1-week retest. Nicotine (0.125 and 0.250 mg/kg) given on both training and testing days enhanced freezing to the context at 24h. In addition, elevated freezing to the context was seen 1 week post-training in mice previously treated with 0.125 and 0.250 mg/kg nicotine. Thus, nicotine-treated mice did show elevated levels of freezing when retested 1 week later, even though no nicotine was administered at the 1-week retest. Mice that received nicotine on training day or testing day only and mice that received nicotine with mecamylamine, a nicotinic receptor antagonist, were not different from saline-treated mice. In addition, post-training administration of nicotine did not enhance fear conditioning. The present results indicate that nicotine enhancement of contextual fear conditioning depends on administration of nicotine on training and test days but results in a long-lasting enhancement of memories of contextual fear conditioning that remains in the absence of nicotine.     

Age-related impairment in the 250-millisecond delay eyeblink classical conditioning procedure in C57BL/6 mice

In this study we tested 4-, 9-, 12-, and 18-month-old C57BL/6 mice in the 250-msec delay eyeblink classical conditioning procedure to study age-related changes in a form of associative learning. The short life expectancy of mice, complete knowledge about the mouse genome, and the availability of transgenic and knock-out mouse models of age-related impairments make the mouse an excellent species for expanding knowledge on the neurobiologically and behaviorally well-characterized eyeblink classical conditioning paradigm. Based on previous research with delay eyeblink conditioning in rabbits and humans, we predicted that mice would be impaired on this cerebellar-dependent associative learning task in middle-age, at ~9 months. To fully examine age differences in behavior in mice, we used a battery of additional behavioral measures with which to compare young and older mice. These behaviors included the acoustic startle response, prepulse inhibition, rotorod, and the Morris water maze. Mice began to show impairment in cerebellar-dependent tasks such as rotorod and eyeblink conditioning at 9 to 12 months of age. Performance in hippocampally dependent tasks was not impaired in any group, including 18-month-old mice. These results in mice support results in other species, indicating that cerebellar-dependent tasks show age-related deficits earlier in adulthood than do hippocampally dependent tasks.     

C57 mice increase wheel-running behavior following stress: preliminary findings

Exercise has been shown to reduce anxiety in both humans and animals. To date, there are few, if any studies that examine the effect of stress on self-selected exercise using an animal model. This study examined the effect of acute stress on wheel-running distance in mice. Forty 8-week-old, male C57BL/6J mice were randomly assigned to one of three groups: no stress + wheel-running experience, stress + wheel-running experience, or stress with no wheel-running experience. Stressed mice were exposed to foot shock in a brightly lit environment. Following treatment, wheel-running distances were observed for three hours. Stress significantly increased voluntary wheel-running in mice with wheel-running experience as compared to nonstressed controls and stressed mice with no wheel-running experience. These results suggest that mice familiar with wheel-running may self-select this exercise as a modality for the mitigation of accumulated anxiety.     

Parent-adolescent reciprocity in negative affect and its relation to early adult social development.

The purposes of this 9-year, prospective longitudinal study were (a) to investigate hypothesized reciprocal growth in negative emotions between parents and adolescents and (b) to examine the influence of this reciprocal process on the development of social relationships during early adulthood. The results showed that both parents' and adolescents' initial levels of negative emotion toward each other predicted the rate of growth and rate of change in growth of expressed negative affect. In addition, the analyses indicated that an adolescent's enmeshment in reciprocal negativity in the family of origin carried over into early adult social relationships. The findings demonstrate the reciprocal nature of negative affect in interactions between parents and adolescents and suggest that family experience with this interactional style may have an adverse influence on the development of early adult social relationships.     

Digital measurement of operant disk press force maintained in CD-1, BALB/c, and C57BL/6 mice

Force of disk press responses by inbred (C57BL/6 and BALB/c) and outbred (CD-1) mice were measured with a PC/DOS-based system, which allowed for continuous measurement of pressing, as well as for control of reinforcer presentation on the basis of response-force dimensions. Photobeam-based measurement of mouse entry into a hopper where reinforcers were presented provided additional information about anticipatory and consumatory behavior in relation to environmental stimuli leading up to reinforcer delivery Disk pressing was generated and measured with the use of an analog-to-digital interface with all three mouse strains. The strains differed in the physical and temporal characteristics of the disk press, as well as in the behavioral chain leading to reinforcer presentation. These measurement methods appear well suited for quantitating functional behavioral differences occasioned by genetic variations in mice.