Cat Madness:

Human Research Using Cats

By Crystal Miller-Spiegel

As I write this article, Gilbert, one of the cats who share my home, is sitting nearby. When I look at him, I cannot imagine how anyone could harm such a wonderful individual. Yet, tens of thousands of cats are used each year in laboratories across the United States, and many more are used worldwide. They are as easy to purchase as inanimate laboratory supplies, and can be found for sale on the internet. And many are still removed from pounds or shelters to be used in lethal research.

According to U.S. Department of Agriculture (USDA) statistics kept from 1973-2000, the peak year for cat use was in 1974 when 74,259 cats were used. The most recent information available indicates that in the year 2000 over 25,500 cats were used in research and testing, and scientists report that 12,354 of these individuals experienced pain and/or distress. These figures do not include cats used in breeding or dissection. Table 1 provides a listing of cat-users, as reported to the USDA in 2000; and Table 2 shows the top ten cat users that same year, including two University of California campuses and pharmaceutical/vaccine manufacturers Pfizer and Fort Dodge. It is important to note that in research areas in which the use of cats is declining, they are often being replaced with smaller, less protected species such as mice and rats.

This article will review some specific areas of research into human conditions and treatments in which felines are often used, most of which are in the field of neurology. In fact, cats have been used so often that they are usually the species of choice because so much is known about their neurological functions. Unfortunately, this type of research is extremely invasive and almost always results in euthanasia of the cats after they are subjected to grueling vivisection procedures.

Spinal Cord Injury

“The [dorsal columns] were completely sectioned in two of these [five] cats…. During the 1st wk subsequent to the lesion, most cats had difficulty in supporting their weight and in walking.”^[1]

Despite their differing locomotion patterns, cats and other animals such as dogs and rats are routinely used as models for spinal cord injuries in humans. Of course, researchers do not use animals whose spinal cords have been damaged accidentally; they actually induce trauma to the spinal cords of healthy cats. Some cats receive treatments, including electrical stimulation, surgical reconstruction, feline fetal central nervous system tissue grafts, and steroids. No effort is made to repair those who serve as the experimental ‘control,’ and studies can last as long as two years. All cats are usually euthanized at the end of the study to examine their brains and spinal cords.

Other cats are injured in order to assess the degree of damage sustained to normal neurological function (i.e., their ability to walk when placed upon a treadmill, maintain balance, control bladder function, etc.) or the accuracy of the method of injury in creating an animal model of spinal cord injury. Methods of intentional spinal cord injury include hot water injury, scalpel or cryogenic lesioning, compressive trauma, electromechanical devices, extradural cuffs, and ‘weight-drop techniques.’ One study on cats and rats conducted at Edward Hines, Jr. Hospital in Illinois concluded that “A stable severe paraplegic state (defined as 6 months for cats…), without evidence of…recovery, was induced by a [15 pound] load [impact force] for cats…. Moderate spinal cord contusion injury, from which cats…partially recovered after approximately 3 months…was induced by a [ten pound]…load.”^[2] A 1996 study also concluded that cats’ spinal cords could be injured by a one-minute exposure to a penetrating radiofrequency electrode set to 149°F.^[3]

Vision

“Amblyopia [‘lazy eye’] will be induced artificially in young kittens by suturing shut the eyelid of one eye. The animals will be allowed to grow up in this situation. It is already known that this will result in the sutured eye losing functional connections with the visual cortex.”^[4]

Cats have long been the subjects of vision research into this malady and other visual impairments such as strabismus (‘cross eye’). As illustrated in this example, the visual problems are not natural but induced by covering the eye with material or stitching the eye shut, and kittens are often used to monitor visual development.

Experimental procedures are also conducted to learn more about the connections between the brain and vision. Cats and other animals are placed in stereotaxic devices, metal devices built to suspend and restrain animals and allow the manipulation of their head or other areas of their body. One study of the cat visual cortex describes the procedure in this manner: “The skull was opened above the portion [of the brain] of area 18 that occupies the lateral gyrus by drilling two semicircular holes…. Fifteen anesthetized paralyzed cats and kittens (10 weeks old) were used.”^[5] In another study, in order to examine living brain slices, eight kittens between the ages of two to three months were injected in the brain, and two weeks later they were anesthetized, a hole was drilled into their skull, and brain tissue from the primary visual cortex was removed.^[6]

In yet another study using 24 cats less than one year old, the cats were anesthetized, and contact lenses were put on their eyes to focus on a computer monitor. The author states, “For optical imaging, the skull was opened…. A stainless-steel chamber was cemented onto the skull, the dura [brain tissue] was removed, and the chamber was filled with silicone oil and sealed with a coverglass.”^[7] A remarkable conclusion was found in another study, which is evident just from the title: “Initial recovery of vision after early monocular deprivation in kittens is faster when both eyes are open.”^[8]

Sleep

“Four adult female…cats were…placed under general anesthesia (halothane), intubated, and restrained in a feline stereotaxic apparatus…. A trephine hole was then drilled into the cranial vault through which a stainless steel cannula was inserted [to allow for multiple extractions of cerebral spinal fluid]…. [After two weeks of recovery] two cats were placed on an enclosed, slow-moving treadmill for 22 hr, thereby enforcing partial sleep deprivation [which was preceded and followed by extraction of spinal fluid].”^[9]

Felines are used as models for sleep and brain function, including sleep disorders and the effects of medication on sleep. To study the effects of morphine on sleep, researchers from Pennsylvania State University injected morphine into the brainstems of six cats and found that it negatively affected secretion of neurotransmitters and disrupted Rapid Eye Movement (REM) sleep, the phase of sleep in which dreaming occurs and which is vital to feel rested.^[10] Several studies of breathing patterns during sleep to understand sleep apnea in humans have been conducted on cats whose brain stems have been severed.

Other Areas

Cancer, Parkinson’s disease, genetic disorders, and auditory studies are some of the other areas in which cats are used as models for human conditions and ailments. The University of Pennsylvania School of Veterinary Medicine maintains a breeding colony of cats with Mucopolysaccharidosis, a genetic disorder that also affects humans. As with studies of visual maladies, scientists intentionally impair cats’ ability to hear, or breed white cats who are genetically predisposed to deafness. After attempting to induce a Parkinsonian-like syndrome in cats with methylphenyltetrahydropyridine (MPTP), an industrial toxin linked to Parkinson’s, researchers chronically implant microelectrode arrays in the cats’ brains for up to 180 days to measure the effects of electrical stimulation.^[11] Another study involved the induction of prolonged cardiac arrest in 10 cats; and after 30 minutes, only six could be resuscitated, and their brains were analyzed for recovery.^[12]

Conclusion

Not only are cats used to test and research new veterinary drugs and treatments, and as models for HIV/AIDS research, but they are also subjected to many troubling procedures, particularly in the vast field of neurological research. Perhaps they are used because they have been characterized so well in the past or because they are small, docile creatures who are easy to obtain or breed and maintain. However, none of these reasons scientifically or ethically justifies their use.

For information on experiments conducted on cats in the New England region of the U.S., visit: http://www.neavs.org/spreadtheword/stw_brochures_cat.htm

Resources

[1] Jiang W. and Drew T. 1996. Effects of bilateral lesions of the dorsolateral funiculi and dorsal columns at the level of the low thoracic spinal cord on the control of locomotion in the adult cat. I. Treadmill walking. J Neurophysiol. 76:849-66.
[2] Khan T., Havey R.M., Sayers S.T., Patwardhan A., and King W.W. 1999. Animal models of spinal cord contusion injuries. Lab Anim Sci 49:161-72.
[3] Haghighi S.S., Perez-Espejo M.A., Rodriguez F., and Clapper A. 1996. Radiofrequency as a lesioning model in experimental spinal cord injury. Spinal Cord 34:214-9.
[4] Schapiro, A.G. Visual Adaptation at Mesopic Light Levels. National Eye Institute Grant Number:1R15EY012946-01. (September 1, 2000 – August 31, 2003).
[5] Shmuel, A. and Grinvald A. 2000. Coexistence of linear zones and pinwheels within orientation maps in cat visual cortex. Proc. Natl. Acad. Sci. USA. 97:5568-5573.
[6] Kojic, L., Dyck, R.H., Gu, Q., Douglas, R.M., Matsubara, J., and Cynader, M.S. 2000. Columnar distribution of serotonin-dependent plasticity within kitten striate cortex. Proc. Natl. Acad. Sci. USA. 97:1841 1844.
[7] Godde, B., Leonhardt, R., Cords,S.M., and Dinse, H.R. 2002. Plasticity of orientation preference maps in the visual cortex of adult cats. Proc. Natl. Acad. Sci. USA. 99:6352 6357.
[8] Mitchell, D.E., Gingras, G., and Kind, P.C. 2001. Initial recovery of vision after early monocular deprivation in kittens is faster when both eyes are open. Proc. Natl. Acad. Sci. USA. 98:11662 11667.
[9] Lerner, R.A., Siuzdak, G., Prospero-Garcia, O., Henriksen, S.J., Boger, D.L., and Cravatt, B.F. 1994. Cerebrodiene: A brain lipid isolated from sleep-deprived cats. Proc. Natl. Acad. Sci. USA. 91:9505-9508.
[10] Anonymous. 1998. Dreamless sleep. New Scientist. 158:25.
[11] McCreery, D.B. Microelectrode Arrays for Deep Brain Stimulation and Recording. National Institute of Neurological Disorders and Stroke Grant Number: 5R01NS040860-03. (September 30, 2000 – August 31, 2003).
[12] Iijima T., Bauer R., and Hossmann K.A. 1993. Brain resuscitation by extracorporeal circulation after prolonged cardiac arrest in cats. Intensive Care Med. 19:82-8

Miller-Spiegel, Crystal. (Winter 2003). AV Magazine. Page 2-7.

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