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Rats will work with vibrating tools: New avenues for animal-based HAVS research.

Wirth-O; Lindsley-WG; Wade-TR; Krajnak-K
10th International Conference on Hand-Arm-Vibration, June 2004, Las Vegas, Nevada. 2004 Jun; :145-146
Introduction: Laboratory animals have been used in multiple ways to study the effects of vibration exposure to limb structures. Some of the effective methods have included vibrating the whole-bodies of rabbits (Kaleta, et al., 1973) and rats (Jurczak, 1974), the tails of rats (Chang et al., 1994; Curry et al., 2002; Hellstrom, 1974; Okada, 1986), or the hind feet of rats (Hansson et al., 1988; Lundborg et al., 1987; Okada et al., 1985) and dogs (Azuma et al.. 1980). Prolonged vibration exposures have provided evidence of damage to vascular structures (Okada et al.. 1987), neural structures (Chang et al., 1994), and muscle (Chang et al., 1994; Necking et al., 1992). Because this damage is thought to underlie the overt symptoms of HAVS (hand-arm vibration syndrome), such as pain, numbness, or loss of sensation, these and similar animal preparations provide alternative means by which the physiological mechanisms of HAVS can be studied experimentally. Invariably, the animals in these preparations must be either anesthetized or physically restrained during the vibration exposure. Although anesthesia and restraint ensure constant and controlled contact between the vibration stimulus and the tailor limb structures, they complicate or even preclude the investigation of some functional and physiological aspects of HAVS development, detection, and prevention. The present paper describes a novel animal preparation for studying HAVS that leaves the animal awake and unrestrained. Method: Twelve male, 12-week-old Sprague-Dawley rats were food restricted to 80% of their free-feeding weight. Operant test chambers were equipped with a custom-designed pull-bar assembly that allowed for the continuous, real-time recording of pull force (Figure I). The bar was positioned in a horizontal orientation and vibrated at 63 Hz, 147 m/s2 along the vertical axis via the attached shaker. Initial training occurred in the first 2 weeks with no vibration. Each rat was trained to pull a bar to receive food pellets. Across sessions, the time between pellet deliveries increased until a response produced a pellet, on average, every 45s. Training sessions ended after the delivery of 100 pellets. On the vibration exposure day, the session began with no vibration and, following every reinforcer thereafter, the magnitude of vibration was increased by increments of 4.9 m/s2 up to a maximum of 147 m/s2, where it remained for the remainder of the session. Exposure sessions lasted 5 hr or until no responding occurred for at least 15 min, whichever came first. Results and Discussion: All rats voluntarily and repeatedly pulled on a vibrating bar to achieve an acute vibration exposure similar to those studied with other preparations. Numerous repetitions occurred during the exposure session that resulted in up to approximately 2 hr of cumulative contact with the vibration. Minor adjustments to the response requirements and schedule of reinforcement can allow for longer exposures or multiple sessions to achieve prolonged vibration exposures across several days, weeks, or even months. The present model has a number of advantages over previously described animal models. For example, by using a volitional model of HA VS we can determine the functional and biological effects of vibration in the absence of additional stress or changes caused by anesthesia or restraint. We also can determine how various exposure variables, such as pull force and posture, affect the probability of developing HAVs. Finally, by exposing the forelimbs to vibration, we can study the effects of vibration that are specifically related to changes in the upper half of the body. By targeting the forelimb, for example, we can study the mechanisms underlying thoracic outlet syndrome, and other vibration-induced disorders that may be caused by changes in the cervico-thoracic autonomic ganglia and associated neural pathways.
Laboratory-animals; Animals; Animal-studies; Vibration; Vibration-exposure; Vibration-disease; Extremities
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10th International Conference on Hand-Arm-Vibration, June 2004, Las Vegas, Nevada