1982; Lukas and Moreton, 1979; Meisch and Lemaire, 1993). The catheter is arranged to exit 
from a site on the back (typical in monkeys) or the top of the head (typical in rats and cats). 
Then the catheter is threaded through a protective device, referred to as a tether, and the tether 
is connected to a swivel. The tubing emerges from the swivel and is connected to a pump, 
which is used to deliver the drug. Monkeys that have been fitted with chronic indwelling 
catheters often wear specially designed vests, shirts, or harnesses to protect the catheter exit 
site. Special procedures (e.g., using antiseptic or aseptic precautions when connecting the end 
of the catheter to the swivel) are carefully planned to maintain the animal in good health and 
maximize the life of the catheter. 
Experiments that require presentation of electrical stimuli to the brain or recording changes in 
sleep and wakefulness involve equipping the animal with a chronic indwelling centrally 
implanted electrode. Some experiments require one or more chronically indwelling cannulae 
in a ventricle or other specific region of the brain (e.g., those involving central drug injection 
or in vivo microdialysis) (Barrett, 1991; Goeders and Smith, 1987). Typically, connection to 
the tether or tubing is made at the beginning of the experimental session and removed at the 
end when the animal is returned to the home cage. 
When experimental conditions must remain in effect for 24 hours at a time, animals with 
chronically indwelling catheters live in the experimental chamber, or the home cage is 
equipped with an intelligence panel to permit presentation of stimuli and recording of 
responses. 
CONSIDERATIONS 
Many forms of restraint and many different kinds of experiments are acceptable as long as the 
particular procedures for inducing and monitoring restraint are well justified, minimized as 
much as possible, and consistent with the ILAR Report (ILAR, 1996). Sometimes the behavior 
of interest is exploration of a novel environment (e.g., open field activity measures in rodents). 
In other cases, exposure to restraint may be an independent variable in an experiment (e.g., to 
take physiological measures believed to be affected by unfamiliar restraint). In many of the 
cases described above, however, a habituation phase is carried out before the experiment itself 
begins. Because animals in behavioral experiments are handled frequently (often five or even 
seven days a week), they usually become habituated quickly to the procedures of transfer to 
the experimental apparatus or chair and to procedures of attaching and removing tethers. 
The habituation phase is especially important for experiments that will involve the greater 
restriction on movement. For example, habituation of a monkey to a shirt/harness/tether 
arrangement is best carried out well in advance of the planned date for implantation of the 
catheter. Inspection of the animal periodically during this habituation process allows the 
experimenter to determine if the vest fits well and permits adjustments to prevent chafing. 
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