range research contribution of each animal, it might be necessary to use animals in multiple protocols that involve surgery. IACUC participation in making these decisions is very important. The well-being of the animals is not necessarily compromised by this approach if careful attention is given to the use of analgesics and enough time is allowed for recovery between operations.1

Conditions Involving Pain

Pain involves stimulation of physiological systems that process information about tissue damage (this process is called nociception) and systems that contribute to the perception of such events as painful. The two kinds of systems are not necessarily both active in all situations (Wall 1979). Nevertheless, the most conservative stance with respect to pain in nonhuman primates is to consider that both systems are operative. As stated in Principle IV of the U.S. Government Principles for the Utilization and Care of Vertebrate Animals Used in Testing, Research, and Training, "Unless the contrary is established, investigators should consider that procedures that cause pain or distress in human beings may cause pain and distress in other animals." (IRAC 1985; NRC 1992, 1996). Accordingly, we should assume that pain is potentially stressful for these animals and that severe or prolonged pain can threaten their psychological well-being.

Pain can occur in research animals for several reasons. It can be an unintended and unwanted byproduct of research. It can be an integral and explicit part of a research protocol, although not an objective (such as the use of electric shock in avoidance conditioning). It can occur as the principal focus of the research, as in experimental studies of pain itself and analgesia. Whatever its source, pain should be carefully monitored and controlled. Pain can occur as an unintended byproduct of research because of deficiencies in the design of equipment or as a postoperative response to surgery. In the first instance, equipment redesign is mandated; in the second, appropriate use of drugs is required (NRC 1992). When pain is used to motivate behavior or in experimental investigations of the nature and treatment of pain, the recommended procedure is to allow the animal to control the amount of pain it receives. For example, it might choose not to perform when the level of aversive stimulation is unacceptable or choose to avoid or escape from a painful stimulus. In any protocol involving the use of pain, the investigator should assess the pain by actually experiencing the maximal stimulus that would be delivered to the animal (NRC 1992).

1  

Before approving multiple major surgery on a single animal, readers should refer to the Animal Welfare Regulations, the Public Health Service Policy, and the Guide. Institutions are prohibited by federal law from conducting multiple major survival procedures on a single animal unless the procedures are components of a single approved protocol. Approval might be granted under exceptional circumstances.



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