For over a century, the laboratory rat, Rattus norvegicus, has been a constant presence in biomedical research. Its contribution to scientific progress is immense, forming a foundation for our understanding of health and disease. This species has been instrumental in developing countless medical treatments and therapies. The story of modern medicine is intertwined with the history of this animal model.
Biological Suitability for Research
The primary reason for the rat’s use in research is its significant biological similarity to humans. Rats and humans share a large portion of their genome, and almost all human genes known to be associated with diseases have counterparts in the rat genome. This genetic closeness means rats can accurately model many human diseases, as their nervous, cardiovascular, and immune systems function in ways comparable to our own.
Beyond genetics, rats offer practical advantages for laboratory settings. Their small size makes them easy and cost-effective to house and care for. A short lifespan and rapid reproductive cycle also allow scientists to conduct multi-generational studies in a fraction of the time it would take with longer-lived species.
Rats possess a high degree of intelligence and exhibit complex social behaviors, which makes them useful for neurological and psychological research. Their ability to learn tasks and navigate mazes provides insight into the mechanisms of learning and memory. Because their brains have structures similar to human brains, they serve as effective models for studying behavior and the effects of drugs on the central nervous system.
Specialized Strains for Scientific Studies
The term “laboratory rat” does not refer to a single type of animal but encompasses a wide variety of specialized strains selectively bred for specific research purposes. This genetic diversity allows scientists to choose a model best suited for their study. Decades of controlled breeding have resulted in numerous inbred and outbred stocks with distinct characteristics.
Among the most common outbred strains is the Wistar rat, one of the first domesticated rat strains. These albino rats are used in a broad range of research, including infectious disease and surgical modeling. Another widely used albino strain is the Sprague Dawley, which is favored for its calm temperament, making it suitable for behavioral, toxicological, and pharmacological studies.
The Long-Evans rat, recognizable by its black-hooded coat, is another outbred strain used in behavioral and neurological research. In addition to these outbred stocks, there are many inbred strains where animals are nearly genetically identical. Strains like the Spontaneously Hypertensive Rat (SHR) naturally develop high blood pressure, serving as a model for cardiovascular research, while the Fischer 344 is used in cancer and aging research.
Major Contributions to Human Health
Research using laboratory rats has led to foundational discoveries that improved human health. In nutrition, early studies with rats were instrumental in identifying essential vitamins and minerals, leading to the prevention of deficiency diseases. This work established the basis for modern nutritional science and dietary guidelines.
In pharmacology and toxicology, rats are essential for testing the safety and efficacy of new drugs before they proceed to human trials. Countless medications, from cholesterol-lowering statins to cancer treatments, have been developed based on data from rat models. Their physiological response to chemical compounds helps scientists determine safe dosage levels and identify potential side effects.
The contributions of rat models to psychology and neuroscience have been significant. Studies on learning, memory, and addiction in rats have provided insights into the workings of the brain. For example, research with rats helped reveal the brain pathways involved in drug addiction, changing the understanding of it from a moral failing to a brain disease. Rat models have also been used to develop cancer therapies and understand conditions like hypertension.
Husbandry and Ethical Guidelines
The use of rats in research is governed by strict ethical guidelines and regulations to ensure their welfare. A central framework is the principle of the “Three Rs”: Replacement, Reduction, and Refinement. Replacement encourages using non-animal methods whenever possible. Reduction aims to minimize the number of animals used, and Refinement involves modifying procedures to minimize potential pain or distress.
In the United States, the Animal Welfare Act and the Public Health Service Policy on Humane Care and Use of Laboratory Animals set standards for animal care. All institutions conducting research with animals must have an Institutional Animal Care and Use Committee (IACUC). This committee, which includes veterinarians and public members, reviews and approves research protocols to ensure they meet ethical standards.
Laboratory rats are housed in controlled environments to protect their health and ensure the reliability of research data. This includes maintaining specific temperature and humidity levels, providing clean air, and managing light cycles. Their diet consists of specially formulated chow, and fresh water is always available. To promote well-being, environmental enrichment like nesting materials and hiding structures is provided to allow for natural behaviors.