xkcd
Campaigns
TS-Si supports open and immediate access to publicly funded research.
Petition: remove women of transsexual / intersex history from the GLAAD Media Reference Guide. [ sign ]
Read: Andrea Rosenfield's call for reform.
Opening Doors to Transsexual Medical Research
TS-Si
is dedicated to the acceptance, medical
treatment, and legal
protection of individuals correcting the misalignment
of their brains and their anatomical sex, while supporting their transition
into society as hormonally reconstituted and surgically corrected citizens.
is dedicated to the acceptance, medical
treatment, and legal
protection of individuals correcting the misalignment
of their brains and their anatomical sex, while supporting their transition
into society as hormonally reconstituted and surgically corrected citizens.
| Raging Mice: Male Aggression As Rewarding As Sex, Food And Drugs |
 |
 |
| SciMed - Neuroscience | |||
| TS-Si News Service | |||
| Tuesday, 15 January 2008 20:00 | |||
London, United Kingdom. New findings argue for the persistence of sex-linked chromosomes, such as the male Y  chromosome, refuting theories that the Y is doomed to extinction.
The results confirm that although these chromosom... brain processes aggression as a reward — much like sex, food and drugs. The new findings, published in the journal Psychopharmacology, offers insights into our propensity to fight and our fascination with violent sports like boxing and football. The rewarding effect of aggression is reduced by nucleus accumbens dopamine receptor antagonism in mice. Maria H. Couppis and Craig H. Kennedy. Psychopharmacology. ISSN 0033-3158 (Print); 1432-2072 (Online). doi 10.1007/s00213-007-1054-y.
Dopamine is a phenethylamine that occurs in both vertebrates and invertebrates. It activates receptors in the brain (neurotransmission) and is also a neurohormone released by the
hypothalamus to inhibit prolactin release from the pituitary's anterior lobe. Rewarding stimuli, such as food, sex and drugs, can stimulate dopamine production. The question before the researchers was whether dopamine has a role in the reinforcement of aggression.  For the experiments, a pair of mice — one male, one female — was kept in one cage and five intruder” mice were kept in a separate cage. The female mouse was temporarily removed, and an intruder mouse was introduced in its place, triggering an aggressive response by the “home” male mouse. Aggressive behavior included tail rattle, an aggressive sideways stance, boxing and biting. The home mouse was then trained to poke a target with its nose to get the intruder to return, at which point it again behaved aggressively toward it. The home mouse consistently poked the trigger, which was presented once a day, indicating it experienced the aggressive encounter with the intruder as a reward.
The same home mice were then treated with a drug that suppressed their dopamine receptors. After this treatment, they decreased the frequency with which they instigated the intruder’s entry.
In a separate experiment, the mice were treated with the dopamine receptor suppressors again and their movements in an open cage were observed. They showed no significant changes in overall movement compared to times when they had not received the drugs. This was done to demonstrate that their decreased aggression in the previous experiment was not caused by overall lethargy in response to the drug, a problem that had confounded previous experiments.
 Maria Couppis conducted her research in affiliation with the Vanderbilt Brain Institute. She is also affiliated with the Vanderbilt Kennedy Center for Research on Human Development and the Vanderbilt Center for Integrative and Cognitive Neuroscience.
“It is well known that dopamine is produced in response to rewarding stimuli such as food, sex and drugs of abuse,” Maria Couppis, who conducted the study as her doctoral thesis at Vanderbilt, said. “What we have now found is that it also serves as positive reinforcement for aggression.”
 Craig Kennedy is chair of Vanderbilt’s Peabody College of Education and human development’s special education department and director of the Behavior Analysis Clinic at the Vanderbilt Kennedy Center for Research on Human Development. “We learned from these experiments that an individual will intentionally seek out an aggressive encounter solely because they experience a rewarding sensation from it,” Kennedy said. “This shows for the first time that aggression, on its own, is motivating, and that the well-known positive reinforcer dopamine plays a critical role.” The rewarding effect of aggression is reduced by nucleus accumbens dopamine receptor antagonism in mice. Maria H. Couppis and Craig H. Kennedy. Psychopharmacology. ISSN 0033-3158 (Print); 1432-2072 (Online). doi 10.1007/s00213-007-1054-y.
Abstract
Rationale. Dopamine (DA) receptors within the nucleus accumbens (NAc) are implicated in the rewarding properties of stimuli. Aggressive behavior can be reinforcing but the involvement of NAc DA in the reinforcing effects of aggression has yet to be demonstrated.
Objective. To microinject DA receptor antagonists into the NAc to dissociate their effects on reinforcement from their effects on aggressive behavior and general movement.
Materials and methods. Male Swiss Webster mice were implanted with guide cannulae aimed for the NAc and tested for aggressive behavior in a resident–intruder procedure. Aggressive mice were then conditioned on a variable-ratio 5 (VR-5) schedule with presentation of the intruder as the reinforcing event. The D1- and D2-like receptor antagonists SCH-23390 and sulpiride were microinfused (12–50 ng) before the mice responded on the VR-5 schedule and attacked the intruder. Open-field activity was also determined following the highest doses of these drugs.
Results. SCH-23390 and sulpiride dose-dependently reduced VR responding but did not affect open-field activity. The 50-ng SCH-23390 dose suppressed response rates by 40% and biting behaviors by 10%; other aggressive behaviors were not affected. The 25 and 50 ng sulpiride doses almost completely inhibited VR responding; the 50-ng dose suppressed biting by 50%.
Conclusions. These results suggest that both D1- and D2-like receptors in the ventral striatum are involved in the rewarding properties of aggression, but that D1-like receptors may be related to the motivation to earn reinforcement as opposed to aggressive behavior.
 The TS-Si News Service is a collaborative effort by TS-Si.org editors, contributors, and corresponding institutions. Sources can include the cited individuals and organizations, as well as TS-Si.org staff contributions. Articles and news reports do not necessarily convey official positions of TS-Si, its partners, or affiliates. We welcome your comments. Use the form below to leave a public comment or send private correspondence via the TS-Si Contact Page. We will not divulge any personal details or place you on a mailing list without your permission.TS-Si is dedicated to the acceptance, medical treatment, and legal protection of individuals correcting the misalignment of their brains and their anatomical sex, while supporting their transition into society as hormonally reconstituted and surgically corrected citizens.
Email this
Comments (0)
 Write comment
|
|||
| Last Updated on Wednesday, 16 January 2008 19:45 |
Subscribe to this comment's feed
Show/hide comments
Show/hide comment form
The TS-Si News Service
and the TS-Si Research Service are collaborations of TS-Si officials, staff, contributors, and corresponding institutions. The contents do not necessarily convey official positions of TS-Si or its owners, participants, partners, or affiliates.