The term “murine” is a common classification in biology and medicine that refers to a specific group of mammals frequently used in scientific inquiry. Understanding this term is central to appreciating a significant portion of modern research, from drug development to understanding genetic diseases. Murine models, particularly mice and rats, serve as indispensable tools that bridge the gap between abstract biological theory and human application.
Defining the Term Murine
The adjective “murine” refers to mice or rats, which are classified together within the family Muridae. This large family is part of the order Rodentia, encompassing a vast number of species worldwide. In scientific practice, however, the term is highly specific, almost exclusively referring to the common house mouse (Mus musculus) and the brown rat (Rattus norvegicus).
These two species have been domesticated and selectively bred for laboratory use, resulting in genetically consistent strains. When researchers discuss “murine models,” they are referring to these laboratory-adapted rodents used as surrogates for human biology. They play a foundational role in preclinical studies and basic biological research.
Why Murine Models are Essential for Science
Murine models are widely used because they possess a combination of biological and logistical characteristics that make them ideal for controlled experimentation. A primary factor is the high degree of genetic and physiological similarity they share with humans. Approximately 95% of the genes that code for proteins in humans have a corresponding gene in the mouse genome, allowing researchers to study human disease mechanisms in a living organism.
Their rapid life cycle is a significant advantage, as a typical mouse lifespan is only about two to three years. This enables scientists to study the progression of diseases and the effects of interventions across an entire lifespan. Mice also have a short gestation period and produce large litters, allowing for the fast breeding of specific, genetically identical strains and quick study across multiple generations.
Logistically, these animals are relatively small, easy to house, and inexpensive to maintain in large numbers under standardized laboratory conditions. Their small size means that drug dosages and reagent costs are much lower compared to larger animal models. This makes large-scale screening and toxicology studies economically feasible.
Scientists have developed extensive tools and techniques to genetically manipulate mice. This includes creating “knockout” models where a specific gene is inactivated. Such manipulation is invaluable for understanding gene function and disease pathology.
Key Differences Between Mice and Rats in Research
Mice and rats are utilized differently based on their distinct biological and behavioral characteristics. Mice are the preferred model for genetic research because the technology for gene manipulation, including transgenic and knockout models, is far more advanced and accessible. Their smaller size also makes them cost-effective for large-scale drug efficacy testing and studies requiring limited amounts of a test compound.
Rats are often favored for complex surgical procedures, cardiovascular studies, and neuroscientific research, as they can weigh up to ten times more than mice. Their larger body size and more defined anatomical features make it easier to perform delicate surgeries, implant monitoring devices, and collect larger volumes of biological samples. Rats also exhibit more complex cognitive behaviors and are generally better at maze-learning tasks, making them superior models for certain addiction and behavioral studies.
Rats are generally easier to handle and show less stress when managed by researchers, which can reduce variability in behavioral experiments. Their larger size also provides better resolution for certain imaging techniques, such as magnetic resonance imaging (MRI). Ultimately, the choice between a mouse and a rat is a deliberate decision based on the specific research question, required surgical accessibility, and the need for genetic manipulability.