eed to use NMBDs must be explained in an investigator’s animal-use protocol and approved by the IACUC (NRC, 1996). Principle V of the US Government Principles (IRAC, 1985) states that “surgical or other painful procedures should not be performed on unanesthetized animals paralyzed by chemical agents,” and the Guide further states (p. 65): Neuromuscular blocking drugs . . . do not provide relief from pain. They are used to paralyze skeletal muscles while an animal is fully anesthetized. They
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might be used in properly ventilated conscious animals for specific types of nonpainful, well-controlled neurophysiologic studies. However, it is imperative that any such proposed use be carefully evaluated by the IACUC to ensure the well-being of the animal because acute stress is believed to be a consequence of paralysis in a conscious state and it is known that humans, if conscious, can experience distress when paralyzed with these drugs (NIH, 1991; NRC, 1992). The special concerns associated with prolonged nonsurvival experiments were well summarized in Preparation and Maintenance of Higher Mammals During Neuroscience Experiments (NIH, 1991): The most critical issues in prolonged nonsurvival experiments arise in the context of anesthesia, maintenance of physiological state, and monitoring of the animal’s condition. The choice of anesthetic must jointly satisfy the need of the experimenter to perturb the preparation as little as possible and his/her obligation to ensure that the animal remains free of pain and distress. Maintaining an anesthetized (and often immobilized) animal in sound physiological condition for several days is a considerable challenge and monitoring both the anesthesia and the animal’s general condition requires careful attention to a number of kinds of measurement. A variety of experimental protocols have been used to minimize the difficulties. The Guide should be interpreted as a flexible document in reviewing protocols of this sort, because procedures may vary with species and among different experimental paradigms. The chief animal welfare concern associated with anesthetized paralyzed animals is that the behavioral indicators of pain and/or distress are inhibited by NMBDs, and this makes it necessary to use special measures to monitor and regulate anesthesia (Gibbs et al., 1989). Anesthesia must be regulated in such a manner that it exerts either no effect or a minimal and constant effect on the neurophysiologic responses being measured. Of both animal welfare and scientific concern is the problem of monitoring and maintaining the animal’s physiologic state, particularly in experiments that extend over several days (Lipman et al., 1997). Issues can also arise regarding infection, in that it usually is not possible to conduct prolonged nonsurvival neuroscience experiments aseptically and the duration of these experiments is sufficient to allow infections to develop. A two-step paradigm is used in most prolonged nonsurvival neuroscience experiments. In one kind of study, during an initial step of 2–4 hours duration, the animal is surgically prepared for a subsequent data collection step, which follows immediately and can last for a few hours to several days (NIH, 1991). During the initial surgical preparation step, all procedures are completed under surgical anesthesia without NMBDs, and analgesics may be administered preemptively to augment the anesthetic regimen (see “Anesthesia and Analgesia” in Chapter 3). Other studies employ a variant of the two-step paradigm that involves performing, several days before the nonsurvival recording session, a survival surgery step during which various devices are implanted (such as a cranial pedestal and cham-
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ber that are used to secure the animal and the recording device, respectively) (NIH, 1991) (see “Multiple Survival Surgeries” in Chapter 4). The latter approach frequently allows the neuroscientist to perform the initial-survival surgery step with aseptic techniques in a dedicated surgical facility. Furthermore, only minor procedures 