The role of endocrines in isolation-induced lntermale fighting in albino laboratory mice. II. Sex steroid influences in aggressive mice

Isolation-induced intermale fighting in laboratory mice can be dramatically reduced under most circumstances by castration. This behavior in castrates may, however, be restored, or even accentuated, by androgen replacement. Experiments on the effects of sex steroids on such fighting in castrated mice, which, for want of a better term, are designated as “aggressive,” have been recently described. These mice are housed with a female until 10 days after siring a litter and are, thereafter, housed individually for a further 14 days before castration and subsequent hormone treatment. Such mice show substantial levels of fighting in “standard-opponent” tests even before isolation. Although castration results in reduced fighting in these mice, this behavior is rarely completely abolished in all individuals. It seems likely that steroid treatment of aggressive mice maintains or intensifies an already present motivation. Treatments in these studies consisted of daily oil-based intramuscular injections for 14 days preceding and throughout behavioral testing. The standard-opponent tests were 7 min encounters with adult, subordinate, grouped males in the cleaned home cages of experimental mice. The steroids investigated included estradiol benzoate (EB), 19-hydroxytestosterone (19-OHT), androstenedione (A), testosterone (T), and Sα-dihydrotestosterone (DHT), either singly or in combination. The results suggest that (a) on a dosage basis, estrogens were at least as effective as androgens in maintaining fighting in castrated aggressive mice; (b) 19-OHT (one of the metabolic intermediates between testosterone and 17 β-estradiol) was also effective but somewhat less so than the same dose of EB; (c) the three naturally occurring androgens investigated all effectively maintained fighting at comparatively low doses (50 μg/day) which compares with a replacement dose of 500 μg/day of T in some studies in traditional castrated mice (e.g., Luttge and Hall, 1973); (d) aromatization is not essential for a behavioral action of androgens as DHT, a nonaromatizable androgen, maintained fighting in these mice; (e) whereas a two-site (central motivational and peripheral penile) action seems probable in the influence of androgens on sexual behavior in castrated rats (e.g., Parrott, 1975), DHT did not augment the action of EB on fighting in castrated aggressive mice, indicating that only a central action of steroids was required in the aggressor.     

Effects of age at differential housing and the duration of individual housing/grouping on lntermale fighting behavior and adrenocortical activity in TO strain mice

A study of the effects of the duration of individual and group housing on intermale fighting and adrenocortical activity was conducted in TO strain mice. It was found that fighting and threat increased with progressive isolation up to an asymptote at 56–58 days. ‘Basal’ adrenocortical function differed little under the 2 housing conditions, but after ‘stress,’ mice isolated for short periods, which had not fought when tested for aggression, had lower titers than group-housed counterparts. However, mice that had been isolated for longer periods, and had fought in aggression tests, had higher corticosterone titers than comparable group-housed animals. The effects of a short duration (28–30 days) of differential housing, commencing at different ages, were also studied. The shorter duration adrenocortical changes were largely confirmed. In general, the earlier the age at which the differential housing was imposed, the greater the behavioral differences between animals under each housing condition. It is suggested that this is largely a consequence of a loss of behavioral plasticity in older mice. The data provides little support for the concept of the “isolation stress syndrome,” or for the view that the characteristic fighting exhibited by individually housed mice is a consequence of “social deprivation”.     

Comparison of agonistic behavior in individually-housed male mice with those cohabiting with females

Videotape recordings of male mice group-housed, individually-housed and cohabiting with females, were rated for their agonistic behavior in a “standard opponent” test. Previously mated male mice showed more fighting than isolated or grouped males. Marked differences in other social and non-social behaviors, which could not be accounted for in terms of increased fighting, were not evident. These results suggest that agonistic behavior may be usefully studied by examining male mice that have cohabited with females. One obvious advantage is that such mice cannot be dismissed as being “socially deprived,” as is sometimes claimed for individually-housed mice. Other advantages are that aggressiveness is induced quickly, at high levels, and the mice appear very sensitive to hormone manipulation following castration.     

A new Method for Determining Reliability Coefficient: The Consistency Index

It was predicted that murderers would differ in their body-image boundary dimensions from attempted suicides. It was found that the murderers obtained lower barrier scores, which was in opposition to the prediction, and lower penetration scores, which was in agreement with the prediction. Overall, therefore, the prediction was not supported.     

Performance on a Mirror-Drawing Task by Non-Right-Handers

Left-, mixed-, and right-handed (each n = 10, N = 30) adolescent boys who were classified on the basis of a hand preference inventory performed a mirror-drawing task with a bilateral transfer of a skill paradigm. Participants' hand preference and the magnitude of bilateral transfer of skill were assessed in terms of errors committed and time taken to complete the mirror-drawing task. Mixed-handed participants exhibited significantly less habit interference for mirror drawing, and they performed the task significantly faster than the left-handers did; the group difference was not significant for the frequency of errors committed. These groups did not differ in terms of the magnitude of bilateral transfer of skill; the trend, however, showed that the transfer of skill was minimum in mixed-handers. These findings extend the theory that mixed-handed participants' inability to transfer motor skill from one hand to the other could be attributable to their lack of a clear pattern of lateralization. Their ability to perform well either at initial or later trials may be a function of less interference from their normal motor habits.     

Effects of acute,subchronic and intermittent MDMA (‘ECSTASY’) administration on agonistic interactions between male mice

Recent studies suggest that acute administration of 3,4‐methylenedioxymethamphetamine (MDMA), an amphetamine derivative popularly known as “ecstasy,” produces an antiaggressive effect in male mice. However, there is no evidence with respect to the development of tolerance or sensitization after its subchronic or intermittent administration. In this study, we examined the action of low to moderate doses of MDMA (1.25, 2.5 and 5 mg/kg, i.p), administered acutely, subchronically (for 7 days) or intermittently, on agonistic behavior elicited by isolation in male mice. Individually housed mice were exposed to anosmic “standard opponents” 30 minutes after the drug administration, and the encounters were videotaped and evaluated using an ethologically based analysis. Acute treatment with MDMA provoked a significant reduction of aggressive behaviors, without altering immobility. However, this action was only selective at 1.25 mg/kg. With the intermediate (2.5 mg/kg) and the highest doses (5 mg/kg) of the drug, it was observed a significant decrease of offensive behaviors, accompanied by an increase of exploration from a distance, avoidance/flee and defense/submission behaviors. This ethopharmacological profile could indicate the existence of an anxiogenic‐like effect of MDMA. The overall picture of the effects of MDMA was very similar in the acutely, intermittently and daily treated animals. No tolerance or sensitization to the actions of the drug was developed after its repeated or intermittent administration.     

Behavioral profile of L–741,741, a selective D4 dopamine receptor antagonist,in social encounters between male mice

Although the role of dopamine D1–D2–D3 receptors in the modulation of aggression has been extensively documented, there is not information with respect to the implication of D4 receptor. The aim of this study was to examine the acute effects of L–741,741 (0.75, 1.5 and 3 mg/kg, i.p), a selective D4 receptor antagonist, on social encounters between male mice using an ethopharmacological approach. Ten min of diadic interactions were staged between a singly housed and an anosmic mouse in a neutral area. These encounters were videotaped and the accumulated time allocated by subjects to ten broad behavioral categories was estimated. Besides other behaviors, the aggressive and motor behaviors were evaluated 30 min after injection using an ethologically based analysis. L–741,741 did not affect significantly offensive behaviors (threat and attack), as compared with the control group. Likewise, motor and anxiety‐related behaviors (such as social investigation, avoidance/flee or defense submission) were not altered after drug administration. These results suggest that dopamine D4 receptor is not involved in the modulation of aggressive behavior. Aggr. Behav. 29:552–557, 2003. © 2003 Wiley‐Liss, Inc.     

尼莫地平改善高钙所致记忆障碍的脑内突触机制

海马内微量注射高钙造成小鼠记忆障碍后,观察了尼莫地平（腹腔注射）对记忆障碍的改善作用,并用透射电镜和图像分析仪对海马CA3区Gray I型突触界面结构参数进行了观测和定量分析,进一步探讨尼莫地平改善高钙所致记忆障碍的脑内突触机制。结果表明,尼莫地平确能改善高钙所致记忆障碍,并能显著逆转高钙所致的小鼠海马CA3区突触间隙宽度显著增大,PSD极显著变薄,平坦型突触显著增多,凹型和穿孔型突触显著减少等一系列突触界面结构的病理性变化。提示海马CA3区Gray I型突触界面结构参数的逆转可能是钙拮抗剂尼莫地平改善高钙所致记忆障碍的形态学基础     

An ethopharmacological assessment of agmatine's effects on agonistic encounters between male mice

The endogenous polyamine agmatine may be a new central neurotransmitter. Agmatine‐like immunoreactivity has been described in numerous brain regions (such as the hypothalamus and amygdala), long thought involved in the control of aggression. Consequently, the present study examined agmatine's (2.5–80 mg/kg, ip) effects on behavior directed by isolated male mice to anosmic partners in a neutral area. The videotaped encounters were analysed in terms of 10 broad behavioral categories. Agmatine did not appear to be involved in the modulation of aggression or anxiety in this test. Aggr. Behav. 31:000000, 2005. © 2005 Wiley‐Liss, Inc.     

Income maximizing in concurrent interval-ratio schedules

Three mice chose between concurrent variable-ratio variable-interval schedules to produce a warm air stream while they were housed in a cold chamber. Across conditions, the duration of the warm air stream was varied between 10 and 80 s and was equal for both schedules. Preference for the VI schedule covaried with reinforcer duration as predicted by maximizing accounts of choice.