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Agonistic behavior of the weakly electric fish, Gnathonemus petersii (Mormyridae, Osteoglossomorpha).

The role played by the electric organ discharge (EOD) in eliciting and maintaining social behavior was assessed. First, a description of the motor acts associated with agonistic encounters between resident and intruder Gnathonemus petersii was provided: The temporal distribution of these acts depended on the aggressiveness of the resident. Second, half of the residents and half of the intruders were rendered electrically "silent" by cutting the nerves to the electric organ. Encounters were staged between pairs of intact fish, pairs of silent fish, and pairs in which one fish was intact and the other silent. Silent residents chased and attacked their opponents less often than the intact fish. Silent and intact residents did not differ in their rates of social probing. Intact intruders elicited higher rates of social probing, and the silent animals elicited more attacks. The effects of the fish's ability to emit EODs and perceive conspecific discharges on different motor acts are discussed.

Aggression↗

Platelet monoamine oxidase activity correlates with social affiliative and agonistic behaviors in normal rhesus monkeys.

After a 4-mo study period, quantitative measures of stable behavioral traits in individual rhesus monkeys correlated significantly with platelet monoamine oxidase (MAO) activity. In particular, behavioral items reflecting social activity and social contact, both agonistic and affiliative, were inversely correlated with enzyme activity. Time spent alone was positively correlated. Since platelet MAO activity is generally stable and predominantly controlled by genetic factors, it might serve as a "genetic marker" for individual differences in "normal" behaviors possibly related to differences in MAO activity in the brain and other tissues.

Age Factors↗

Chronic alterations in serotonin function: dynamic neurochemical properties in agonistic behavior of the crayfish, Orconectes rusticus.

The biogenic amine serotonin [5-hydroxytryptamine (5-HT)] has received considerable attention for its role in behavioral phenomena throughout a broad range of invertebrate and vertebrate taxa. Acute 5-HT infusion decreases the likelihood of crayfish to retreat from dominant opponents. The present study reports the biochemical and behavioral effects resulting from chronic treatment with 5-HT-modifying compounds delivered for up to 5 weeks via silastic tube implants. High performance liquid chromatography with electrochemical detection (HPLC-ED) confirmed that 5,7-dihydroxytryptamine (5,7-DHT) effectively reduced 5-HT in all central nervous system (CNS) areas, except brain, while a concurrent accumulation of the compound was observed in all tissues analyzed. Unexpectedly, two different rates of chronic 5-HT treatment did not increase levels of the amine in the CNS. Behaviorally, 5,7-DHT treated crayfish exhibited no significant differences in measures of aggression. Although treatment with 5-HT did not elevate 5-HT content in the CNS, infusion at a slow rate caused animals to escalate more quickly while 5-HT treatment at a faster rate resulted in slower escalation. 5,7-DHT is commonly used in behavioral pharmacology and the present findings suggest its biochemical properties should be more thoroughly examined. Moreover, the apparent presence of powerful compensatory mechanisms indicates our need to adopt an increasingly dynamic view of the serotonergic bases of behavior like crayfish aggression.

5,7-Dihydroxytryptamine↗

Agonistic behavior in groups of limbic epileptic male rats: pattern of brain damage and moderating effects from normal rats.

Different ratios of normal male rats and male rats in which limbic seizures had been induced by a single systemic injection of lithium and pilocarpine were housed in groups of six. The group ratios ranged along the continuum from all normal rats to all experimental rats. The average numbers of episodes of boxing, biting and mounting--thrusting per rat per hour per group were recorded by direct observation (red light) for 1 h during the midscotophase. Groups that contained less than two normal rats exhibited significantly elevated amounts of agonistic (boxing, biting) behavior but not mounting behavior. Multiple regression analyses showed that combinations of neuronal loss within only two to three areas accommodated at least 50% of the variance in the numbers of these behaviors.

Agonistic Behavior↗

Conceptual and methodological issues in the genetics of mouse agonistic behavior.

Currently, 36 genes have been reported to affect offensive behavior in male mice. Potentially, these genes could be used to analyze the mechanism of this behavior. But there are methodological flies in this conceptual ointment. The studies with these genes varied in the genetic background, the maternal environments, the postweaning housing, the strain or type of opponent, and the type of test. The effects of each of these on the genetics of offense are reviewed with examples. It is concluded that between-study variation in these environmental or experiential circumstances may make it difficult to impossible to relate the effect of one genetic variant to another and to use these to identify and relate the pathways for gene effects on offensive behaviors. For this reason, standardization of these conditions is recommended.

Agonistic Behavior↗

Lead exposure alters the development of agonistic behavior in golden hamsters.

We tested the effects of exposure to different doses of lead acetate (either 0, 25, 100, or 400 ppm) on the development of aggressive behavior in male golden hamsters. Pups were tested for offensive responses across puberty, as they were maturing from play fighting to adult aggression. Our data show a dose-specific effect of lead exposure on the development of aggression during puberty at doses resulting in blood levels well below 20 microg/dl. Animals exposed to 25 ppm lead acetate were faster and performed more than twice as many attacks on intruders by late puberty. They were also twice as likely to initiate adult instead of play-fighting attacks around mid-puberty. These observations were independent of any effect on growth. Thus, exposure to low doses of lead enhanced aggression and accelerated its maturation. As such, our data support the association between exposure to low doses of lead and aggressive behavior in boys.

Agonistic Behavior↗