Opportunity for aggression as a reinforcer in mice (original) (raw)
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There is evidence suggesting aggression may be a positive reinforcer in many species. However, only a few studies have examined the characteristics of aggression as a positive reinforcer in mice. Four types of reinforcement schedules were examined in the current experiment using male Swiss CFW albino mice in a resident–intruder model of aggression as a positive reinforcer. A nose poke response on an operant conditioning panel was reinforced under fixed-ratio (FR 8), fixed-interval (FI 5-min), progressive ratio (PR 2), or differential reinforcement of low rate behavior reinforcement schedules (DRL 40-s and DRL 80-s). In the FR conditions, nose pokes were maintained by aggression and extinguished when the aggression contingency was removed. There were long postreinforcement pauses followed by bursts of responses with short interresponse times (IRTs). In the FI conditions, nose pokes were maintained by aggression, occurred more frequently as the interval elapsed, and extinguished when the contingency was removed. In the PR conditions, nose pokes were maintained by aggression, postreinforcement pauses increased as the ratio requirement increased, and responding was extinguished when the aggression contingency was removed. In the DRL conditions, the nose poke rate decreased, while the proportional distributions of IRTs and postreinforcement pauses shifted toward longer durations as the DRL interval increased. However, most responses occurred before the minimum IRT interval elapsed, suggesting weak temporal control of behavior. Overall, the findings suggest aggression can be a positive reinforcer for nose poke responses in mice on ratio-and time-based reinforcement schedules.
Surprising nonreward reduces aggressive behavior in rats
International Journal of Comparative Psychology, 2000
Studies with several mammalian species show that the surprising omission of an appetitive reinforcer invigorates aggressive behavior. In the present experiment, dominant and nondominant individuals within pairs of male rats were identified in pretests sessions. The dominant males were then randomly assigned to one of two groups and trained in a consummatory contrast situation. Group 32-W received exposure to 32% sucrose solution and was then shifted to water; Group W-W received exposure to water throughout the experiment. Immediately after a shift to water, nondominant males were introduced in the training box for a 5-min-long session. The previously dominant males of Group 32-W exhibited a significant decrease in aggressive attacks to nondominant pairmates, compared to the W-W dominant rats. Consummatory training in a situation involving surprising nonreward inhibits aggressive behavior. The potential connection between the present results and those obtained in experiments with inescapable shocks is discussed. Rats exposed to a surprising reduction in the magnitude of an appetitive reinforcer not only consume less of the small magnitude than a control group always exposed to the smaller reward (a phenomenon called consummatory successive negative contrast, cSNC), but also exhibit significantly less dominance in social interactions with conspecifics. In one experiment (Mustaca & Martínez, 2000), rats received access to a 32% sucrose solution in 5-min long sessions during several days before being shifted to a 2% solution. Immediately after this postshift session, these animals were allowed interaction with control animals exposed to the 2% solution throughout the experiment. Shifted rats were more likely to be attacked by unshifted controls, than vice versa. Shifted rats were also significantly more attacked by nontrained intruders than unshifted controls. These results stand at variance with published reports indicating that surprising reward loss invigorates mammalian aggressive behavior directed at a conspecific (e.g.
Successful intermale aggression and conditioned place preference in mice
Physiology & Behavior, 1995
MART~IEZ, M., F. GUILLI~N-SALAZAR, A. SALVADOR AND V. M. SIMON. Successful intermale aggression and conditioned place preference in mice. PHYSIOL BEHAV 58(2) 323-328, 1995.--This study assessed the reinforcing properties of successful intermale agonistic encounters between OFI male mice using the conditioned place preference paradigm. A three compartment apparatus was used and the procedure consisted of three phases: preconditioning (3 days), conditioning (8 days) and postconditioning (3 tests). Individually housed male mice were allocated to two groups. The aggression group confronted docile opponents in the preconditioning "less-preferred" compartment and were left alone in the "preferred" one. The control group was left alone in both compartments. Whereas no significant differences were found between both groups in the time spent in the less-preferred compartment, a separate analysis of animals in function of the color of the less-preferred compartment revealed a clear-cut difference. Mice developed a conditioned place preference for the aggression-paired compartment only if that experience took place in the black one. These findings suggest that the process of establishing a conditioned place preference with successful intermale aggression as reinforcer is extremely fragile and can be easily disrupted by changing the environmental cues involved.
We recently developed a conditioned place preference (CPP) procedure, commonly used to study rewarding drug effects, to demonstrate that dominant sexually-experienced CD-1 male mice form CPP to contexts previously associated with defeating subordinate male C57BL/6J mice. Here we further characterized conditioned and unconditioned aggression behavior in CD-1 mice. In Exp. 1 we used CD-1 mice that displayed a variable spectrum of unconditioned aggressive behavior toward younger subordinate C57BL/6J intruder mice. We then trained the CD-1 mice in the CPP procedure where one context was intruder-paired, while a different context was not. We then tested for aggression CPP 1 day after training. In Exp. 2, we tested CD-1 mice for aggression CPP 1 day and 18 days after training. In Exp. 3–4, we trained the CD-1 mice to lever-press for palatable food and tested them for footshock punishment-induced suppression of food-reinforced responding. In Exp. 5, we characterized unconditioned aggression in hybrid CD-1 × C57BL/6J D1-Cre or D2-Cre F1 generation crosses. Persistent aggression CPP was observed in CD-1 mice that either immediately attacked C57BL/6J mice during all screening sessions or mice that gradually developed aggressive behavior during the screening phase. In contrast, CD-1 mice that did not attack the C57BL/6J mice during screening did not develop CPP to contexts previously paired with C57BL/6J mice. The aggressive phenotype did not predict resistance to punishment-induced suppression of food-reinforced responding. CD-1 × D1-Cre or D2-Cre F1 transgenic mice showed strong unconditioned aggression. Our study demonstrates that aggression experience causes persistent CPP and introduces transgenic mice for circuit studies of aggression.
An anxiety-like phenotype in mice selectively bred for aggression
Behavioural Brain Research, 2009
Using selective bi-directional breeding procedures, two different lines of mice were developed. The NC900 line is highly reactive and attacks their social partners without provocation, whereas aggression in NC100 animals is uncommon in social environments. The enhanced reactivity of NC900 mice suggests that emotionality may have been selected with aggression. As certain forms of anxiety promote exaggerated defensive responses, we tested NC900 mice for the presence of an anxiety-like phenotype. In the open field, light-dark exploration, and zero maze tests, NC900 mice displayed anxiety-like responses. These animals were less responsive to the anxiolytic actions of diazepam in the zero maze than NC100 animals; diazepam also reduced the reactivity and attack behaviors of NC900 mice. The NC900 mice had reduced diazepam-sensitive GABA A receptor binding in brain regions associated with aggression and anxiety. Importantly, there was a selective reduction in levels of the GABA A receptor ␣ 2 subunit protein in NC900 frontal cortex and amygdala; no changes in ␣ 1 or ␥ 2 subunit proteins were observed. These findings suggest that reductions in the ␣ 2 subunit protein in selected brain regions may underlie the anxiety and aggressive phenotype of NC900 mice. Since anxiety and aggression are comorbid in certain psychiatric conditions, such as borderline personality and posttraumatic stress disorder, investigations with NC900 mice may provide new insights into basic mechanisms that underlie these and related psychiatric conditions. (W.C. Wetsel). 1 Both authors contributed equally to this work.
Modeling fighting deprivation effect in mouse repeated aggression paradigm
Progress in Neuro-Psychopharmacology and Biological Psychiatry, 2011
Male mice with a long positive fighting history develop behavioral psychopathology, which includes abnormal aggression, hostility, hyperactivity, stereotypic reactions and other behavioral phenotypes. We also found that the "winners" (mice that had each won 20 daily encounters in succession) develop an enhanced level of aggression after a no-fight period, compared to their respective levels of aggressive behavior before the fighting deprivation. Natural hedonic stimuli (such as access to females or sweet water), supplied to the winners during this no-fight period, appear to play a minor role in triggering this phenomenon. Therefore, it appears that fighting deprivation per se stimulates an elevated aggression in male mice, which also display aberrant behaviors formed under repeated experience of aggression accompanied by victories. This behavioral approach may be useful for modeling the effect of fighting deprivation in mouse paradigms based on repeated aggression.
Aggressive behavior as a reinforcer in mice: activation by allopregnanolone
Psychopharmacology, 2002
Rationale: The neurobiological mechanisms that underlie the motivation to engage in an aggressive confrontation remain to be investigated. Objective: The objective was to develop a method to differentiate pharmacologically the performance elements of aggressive behavior from behaviors that precede an aggressive encounter. Methods and results: Male CFW mice were housed as "residents" and trained to poke their nose in a hole in a panel placed into the home cage. After fulfilling a specific response requirement, an "intruder" male mouse was introduced for a brief aggressive encounter. In experiment I, the mice were maintained on a fixed ratio schedule of ten responses (FR10) and after stable responding, extinction and stimulus control were assessed by switching the active hole in an ABA design. In experiment II and III, the mice were maintained on a fixed interval schedule of 10 min (FI10 min) and responded with accelerating rates towards the end of the interval (mean index of curvature was 0.37). In experiment III, the mice were given the GABA A receptor positive modulator allopregnanolone (5.6-17 mg/kg or vehicle, IP), before responding on an FI10 min schedule reinforced by a 5-min aggressive encounter. Allopregnanolone had bitonic effects on FI responding and aggressive behavior. The low dose of allopregnanolone nearly doubled overall response rate without affecting the index of curvature, attack bites or sideways threats. The moderate dose increased attack behaviors by about 45% and had little effect on response rate and the index of curvature. In contrast, the higher dose decreased the index of curvature but had no effect on aggressive behavior or overall response rate. Conclusions: These data support previous demonstrations that certain GABA A positive modulators heighten aggressive behavior. Moreover, examining operant responding that is reinforced by the opportunity for aggression, it may be possible to dissociate pharmacological effects on the behaviors leading up to an aggressive encounter from their effects on specific aggressive acts.