Animal Models of Substance Abuse

Nonhuman primates (principally macaques, squirrel monkeys, and baboons) are used as subjects in behavioral and neuropharmacology experiments to study the effects of psychoactive drugs on specific types of behavior and to investigate the potential for abuse and drug dependence that such drugs present (e.g., Barrett 1985; Brady and Lukas 1984; Brady and others 1987; Meisch and Carroll 1987; Yanagita 1987). Some of the research conditions already considered—such as those involving restraint, invasive procedures, and aversive stimulation—are also used in research on psychoactive drugs, and the same concerns apply with respect to psychological well-being. In addition, the creation of physical or psychological drug dependence raises the possibility of intense withdrawal responses that might continue—or even become more severe—when an animal is no longer in the experimental setting. If such effects can be anticipated and are not part of the aims of the research, the IACUC and the investigator are obliged to consider them and if possible mitigate or eliminate them. Subjects in these studies present a special problem in providing for psychological well-being. They are often not compatible with social partners and might be unresponsive to other enrichment techniques, depending on the pharmacological agent being used and the degree of dependence. Their comfort and well-being require special attention and consideration.

Conditions Involving Aggression

Aggression is a part of the lives of nonhuman primates. In its most extreme form, aggression can cause extensive injury or death, and even the milder forms of aggression—which are generally expressed as species-typical postures or facial expressions—can be a marked source of stress. Different types of aggression can be directed toward conspecifics or caregivers, or toward the physical environment. Self-injurious behavior is a special type of behavior of concern.

Although investigators can find many opportunities to study the mechanisms involved in the expression and control of aggression by observing spontaneous outbreaks of aggression, some forms of research into aggression might involve the use of methods that instigate aggression under controlled conditions. That aggression is the subject of an approved study does not relieve the investigator, veterinarian, and IACUC of the responsibility for ensuring that consequent injuries and stress are minimized. Aggressive episodes, whether fortuitously detected or instigated according to an applied protocol, should be carefully monitored and controlled. In both instances, investigators have an obligation to intervene to protect their subjects from harm. When aggression is studied as part of an approved protocol, there should be a clear statement of the criteria to be used in deciding when intervention is necessary and a protocol to follow to keep the risk of injury and the degree of stress to the minimum consistent with the aims of the research. For many research purposes, injury is an unnecessary and undesirable consequence of research on aggression.

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