Aggressive Behavior In Male Rats Research Articles

Soya bean rich diet is associated with adult male rat aggressive behavior: relation to RF amide-related peptide 3-aromatase-neuroestrogen pathway in the brain.

Relation between soya bean (SB) consumption and aggressive behavior has not been elucidated yet. Thus, this study was conducted to investigate the effect of large amount of SB consumption on adult male rats' aggressive behavior through investigating changes in the expression of gonadotropin-inhibitory hormone/ RF amide-related peptide 3 (GnIH/RFRP3), neuropeptide FF receptor, cytochrome P450, family 19, subfamily A, polypeptide 1 (Cyp19A1), estrogen receptors α and β and the levels of neuroestrogen, dopamine, glutamate and testosterone as well as aromatase activity in the brain. Adult male rats were divided into three equal groups: group I, control group, received standard diet; group II and group III received 25% and 50% SB of their standard diet contents, respectively, for 12weeks. The obtained results showed that feeding male rats with large amount of SB could induce aggressive behavior in a dose dependant manner possibly through inhibition of brain GnIH/RFRP-aromatase-neuroestrogen pathway. These effects may be through decreasing aromatase activity, neuroestrogen concentration, Cyp19A1 and ER β mRNA levels and increasing ER α mRNA levels and immunostaining as well as testosterone, dopamine and glutamate levels in the brain. These findings also provide further support for the inhibitory role of RFRP3 on aggressive behavior of male rats. These data may open new avenues for the potential harmful effects of consumption large amounts of SB rich food on humans.

Resident intruder paradigm-induced aggression relieves depressive-like behaviors in male rats subjected to chronic mild stress.

BackgroundAccumulating epidemiological evidence shows that life event stressors are major vulnerability factors for psychiatric diseases such as major depression. It is also well known that the resident intruder paradigm (RIP) results in aggressive behavior in male rats. However, it is not known how resident intruder paradigm-induced aggression affects depressive-like behavior in isolated male rats subjected to chronic mild stress (CMS), which is an animal model of depression.Material/MethodsMale Wistar rats were divided into 3 groups: non-stressed controls, isolated rats subjected to the CMS protocol, and resident intruder paradigm-exposed rats subjected to the CMS protocol.ResultsIn the sucrose intake test, ingestion of a 1% sucrose solution by rats in the CMS group was significantly lower than in control and CMS+RIP rats after 3 weeks of stress. In the open-field test, CMS rats had significantly lower open-field scores compared to control rats. Furthermore, the total scores given the CMS group were significantly lower than in the CMS+RIP rats. In the forced swimming test (FST), the immobility times of CMS rats were significantly longer than those of the control or CMS+RIP rats. However, no differences were observed between controls and CMS+RIP rats.ConclusionsOur data show that aggressive behavior evoked by the resident intruder paradigm could relieve broad-spectrum depressive-like behaviors in isolated adult male rats subjected to CMS.

Genomic and non-genomic effects of glucocorticoids on aggressive behavior in male rats

An increasing body of evidence suggests that glucocorticoids—besides their well-known genomic effects—can affect neuronal function via mechanisms that do not involve the genome. Data obtained mainly in amphibians and birds suggest that such mechanisms play a role in the control of behavior. Acute glucocorticoid treatments increase aggressive behavior in rats, but the mechanism of action has not been investigated to date. To clarify the issue, we have assessed the aggressiveness of male rats after treating them with the corticosterone synthesis inhibitor metyrapone, corticosterone, and the protein synthesis inhibitor cycloheximide. Metyrapone applied intraperitoneally (i.p.) decreased the aggressiveness of residents faced with smaller opponents. Corticosterone administered i.p. 20 or 2 min before a 5-min encounter abolished these changes irrespective of the delay of behavioral testing. Thus, the effects of glucocorticoids on aggressive behavior occurred in less than 7 min (the delay and duration of testing taken together), and lasted more than 25 min. Corticosterone applied centrally (infused into the right lateral ventricle) also stimulated aggressive behavior rapidly, which shows that the effect was centrally mediated. The protein synthesis inhibitor cycloheximide did not affect the aggression-promoting effects of corticosterone when the hormone was injected 2 min before the aggressive encounter. Surprisingly, however, the effects were completely abolished when the hormone was injected 20 min before the encounter. These data suggest that glucocorticoids rapidly increase aggressive behavior via non-genomic mechanisms. In later phases of the aggressive encounter, aggressive behavior appears to be stimulated by genomic mechanisms.

Acute trazodone and quipazine treatment attenuates apomorphine-induced aggressive behaviour in male rats without major impact on emotional behaviour or monoamine content post mortem

We have studied the effect of acute trazodone (3–20 mg kg−1) and quipazine (1–3 mg kg−1) treatment on the apomorphine-induced (1 mg kg−1, once daily over 2 weeks) aggressive behaviour in male Wistar rats. All doses of trazodone and quipazine tested attenuated the aggressiveness as evidenced by the abolished intensity of aggressive behaviour and increased time of latency before the first attack. The acute trazodone (3–10 mg kg−1) or quipazine (1–3 mg kg−1) treatment had no or only a minor effect on rat behaviour in the elevated plus-maze, open field, and forced swimming test. Concomitant apomorphine (1 mg kg−1) plus trazodone (3 mg kg−1), but not apomorphine (1 mg kg−1) plus quipazine (1 mg kg−1), treatment slowed the development of aggressive behaviour. Repeated apomorphine treatment moderately reduced the dopamine post mortem and increased the DOPAC and HVA contents in striatum. Other monoamines or their metabolites were unchanged. Neither trazodone and quipazine treatment nor forced swimming stress induced any changes in the monoamine contents. In conclusion, our results indicate that acute trazodone and quipazine treatment attenuates the apomorphine-induced aggressive behaviour in male rats, but this phenomenon cannot be implicated in the changes in emotional and motivational behaviour, or in changes of monoamine content post mortem.

Modulatory role of 5-HT 3 receptors in mediation of apomorphine-induced aggressive behaviour in male rats

We have studied the effects of serotonin (5-HT) 5-HT 3 receptor agonists 1-phenylbiguanide (1-PBG) and 1-(m-chlorophenyl)-biguanide (mCPBG), and antagonists 3-tropanyl-3,5-dichlorobenzoate (MDL-72222) and tropisetron (3-tropanyl-indole-3-carboxylate HCl; ICS-205930) on apomorphine-induced aggressive behaviour in normal or DSP-4 [ N-(2-chloroethyl)- N-ethyl-2-bromobenzylamine hydrochloride] pre-treated male Wistar rats. DSP-4 (50 mg/kg) pre-treatment significantly accelerated the development of apomorphine-induced aggressive behaviour. mCPBG (1.0 and 10 mg/kg) did not modify the aggressiveness, but 1-PBG (3.0 and 30 mg/kg) attenuated the aggressiveness in normal but not DSP-4 pre-treated rats. MDL-72222 (0.4 and 4.0 mg/kg) attenuated the aggressive behaviour in normal rats, tropisetron (0.3 mg/kg) had an antiaggressive effect only by citalopram (10 mg/kg) challenge. MDL-72222 and tropisetron were ineffective in DSP-4 pre-treated rats. In conclusion, our results indicate that the 5-HT 3 receptors modulate the apomorphine-induced aggressive behaviour and the 5-HT 3 receptor antagonists have moderate antiaggressive effect in this test.

Motivational systems or motivational states: Behavioural and physiological evidence

This paper will critically discuss the available behavioural and neurobiological evidence for the existence of motivational systems and motivational states on the basis of our studies on aggressive behaviour in male rats and mice. Three types of evidence will be discussed. First, some behavioural studies will be evaluated indicating that aggressive behaviour can be considered as part of a cluster of behaviours used to cope actively with environmental challenges. Second, it will be argued that coping styles are based upon different neurochemical brain states, which may be a reflection of motivational states. Third, the neurobiological evidence will be discussed for the existence of identifiable neuronal systems for certain behaviour systems, on the basis of studies on male sexual and aggressive behaviour. Finally, the relevance of the concept of coping styles to stress-pathology will be discussed briefly.

Influence of the mother on development of aggressive behavior in male rats

The present experiments investigated pre- and postnatal maternal effects on aggressive behavior in rats. Resident-intruder aggressive behavior of male rats in colonies (two males and two females) was studied in five experimental groups: 1 = WWY ( n = 7) the two males of each colony were wild (biological father and mother were wild) fostered by a wild mother; 2 = WAY ( n = 11) the two males were wild fostered by an albino Wistar mother; 3 = AAY ( n = 11) the two males were albino (biological father and mother were Wistar) fostered by an albino mother; 4 = AWY ( n = 12) the two males were albino fostered by a wild mother; and 5 = HWX + HAX ( n = 9) one of the males was hybrid born and reared by a wild mother (the father was albino) and the other was also hybrid but born and reared by an albino mother (the father was wild). Each test lasted 10 min and the intruder was always a Wistar male. Aggression of wild rats was higher than the laboratory ones, independently of the mother (albino or wild) they were fostered by. However, hybrid males born and reared by a wild mother were more aggressive than those that were born and reared by an albino mother, in spite of the father being wild. In conclusion, crossfostering has little effect on territorial aggression, but prenatal maternal effects seem to play a major role on the ontogeny of aggressive behavior of male rats.

Ultrasonic vocalizations and aggressive behavior in male rats

The aim of the present study was to know whether 22–28-kHz vocalizations have any communicatory role in the regulation of aggressive behavior in male rats of the Wistar strain. In pairs of intact rats 22–28-kHz vocalizations showed a positive correlation with the extent of aggressive behavior. The pattern of aggressive behavior during ultrasonic vocalizations was different from that just before and just after the vocalizations. However, surgically deafened rats were less active in aggressive behavior and more active in ambulatory activity in the open field than the controls. Muted rats were not different from the controls in both aggressive behavior and ambulatory activity. The present result that the deprivation of ultrasonic signals failed to increase aggressive behavior does not support the classical hypothesis that ultrasonic vocalizations inhibit the initiation of aggressive behavior. It is concluded that ultrasounds emitted during aggressive encounters may have little communicative value in male rats.

Intermale social aggression: Suppression by medial preoptic area lesions

The intermale social aggressive behavior of male rats cohabiting with a female rat was quantitatively scored weekly in response to the introduction of an unfamiliar intruding male. Resident male rats whose aggressiveness toward an intruder reached a criterion level were subjected to either sham lesions or bilateral lesions in the region of the medial preoptic area. The lesioned rats continued to exhibit levels of piloerection and lateral attack that were not significantly lower than those of sham-lesioned animals. However, the lesioned animals did emit significantly fewer bites and spent significantly less time in the “on-top” position than did sham-lesioned animals. The lesioned animals also displayed significantly less sexual behavior than the sham-lesioned animals but were not different in terms of defensiveness toward the experimenter. It is suggested that bilateral lesions in the region of the medial preoptic area cause a decrease in the intensity of intermale social aggression but do not prevent external stimuli from eliciting the aggression.

Effect of anterior hypothalamic and mammillary area lesions on territorial aggressive behaviour in male rats

Adult male Wezob-rats were bilaterally lesioned in either the medial anterior hypothalamic area or the mammillary bodies. The behaviour of these animals when confronted with a male intruder within their own territory, was observed and recorded before and after lesioning and compared with the behaviour of sham-operated animals. Anterior hypothalamic lesions, including large parts of the anterior hypothalamus, the rostral part of the ventromedial hypothalamic nucleus and smaller caudal parts of the preoptic area, led to strong increases in defensive behaviour. This included a decreased tendency to investigate the intruder and an exaggerated defensive reaction when approached by the intruder. Ingestive behaviour and bodyweight were enhanced. Mammillary body lesions, including large parts of the ventral and dorsal premammillary nucleus, the caudal part of the arcuate nucleus, the medial mammillary nucleus, the posterior mammillary nucleus, the supramammillary peduncle and closely surrounding areas, led to a marked increase in offensive behaviour. This was characterized by high levels of initatives and aggression towards an intruder. It is suggested that two distinct neural substrates exist in the medial hypothalamus, which normally modulate defensive (anterior medial hypothalamus) or offensive (posterior medial hypothalamus) aspects of intermale aggression.

The effect of cyproterone acetate on shock elicited aggression in rats

The aggressive behavior of male rats treated chronically with cyproterone acetate was measured following electric footshock. Shock elicited fighting behavior and body weight was recorded once every week for 4 weeks. The level of plasma testosterone, brain 5-HT and 5-HIAA and weight of testes were measured 24 hours after the last injection. No significant change was observed in the level of testosterone or brain 5-HT and 5-HIAA. A trend towards an increase in plasma testesterone and shock elicited fighting in rats treated with a higher dose of CA (10 mg/kg) may be indicative of some androgenic property of CA. On the other hand a slower gain in the body weight and a significant reduction in the testes weight of CA treated rats corroborate the well known antiandrogen property of this steroid. The balance of these androgenic and antiandrogenic properties of CA may absence of significant changes in behavioral and biochemical measures.

Sex pheromones and aggressive behavior in male rats

Two experiments were performed to examine the relationships among the sexual cycle of the female, sex pheromones, and the agonistic behavior of male rats. Data suggest that the presence of an inaccessible sexually receptive female provokes increased intermale fighting. The present research investigated the possibility that a sex pheromone from the female mediates the change in male hostilities. In Experiment 1, a combination between-subject and within-subject design was used to expose half the males to the female by several sensory modalities. The other males were exposed to the female primarily by olfaction. In Experiment 2, a completely between-subject design was used to expose some males only to the soiled bedding of the female. The results suggest that olfaction is sufficient to increase the male’s aggressiveness in the presence of an estrous female, although additional sensory input, such as the female’s movements, may be necessary to produce the full aggression-inducing effect.

Testosterone-estradiol filled polydimethylsiloxane subdermal implants: effect on fertility and masculine sexual and aggressive behavior of male rats.

Testosterone-estradiol filled polydimethylsiloxane subdermal implants: effect on fertility and masculine sexual and aggressive behavior of male rats.