What Are Rats?

Rats, principally the Norway rat Rattus norvegicus, are the most extensively used mammalian model organisms in biomedical and engineering research. Domesticated for laboratory use over 150 years ago, laboratory rat strains have been selectively bred to produce animals with well-characterized genetics, predictable physiology, and body sizes large enough to permit surgical instrumentation, pharmacological manipulation, and electrophysiological recording that would be technically difficult or impossible in smaller rodents such as mice. Inbred strains including Sprague-Dawley, Wistar, and Fischer 344 provide the genetic uniformity required for reproducible experimental results. The rat's nervous system, cardiovascular anatomy, and metabolic physiology closely parallel those of humans in ways that have made it the preferred model for studies of neurological disease, cardiovascular pharmacology, toxicology, and behavioral neuroscience.

The relationship between rats and engineering research extends across several dimensions. Rats serve as subjects for neural recording, brain stimulation, and prosthetic interface experiments. They are the test platform for implantable biosensors, drug delivery devices, and brain-computer interfaces. And they are increasingly the subjects of robotic and computational models designed to simulate or interact with animal behavior.

Rats as Model Organisms

Rats have occupied a central role in biomedical research because they offer a favorable combination of size, cognitive complexity, and genetic tractability. The rat brain, at roughly 2 grams, is large enough to permit multi-electrode array implantation across multiple cortical and subcortical regions simultaneously, enabling the kind of large-scale neural population recordings that have driven systems neuroscience over the past two decades. Research published in PMC on rodent models in neuroscience research describes how the rat's relatively large hippocampus and cortex made it the primary model for place cell and grid cell studies that led to the 2014 Nobel Prize in Physiology or Medicine. The rat also displays complex social behaviors, including play, social transmission of food preferences, and cooperative problem-solving, that make it useful for studying the neural substrates of social cognition.

Mice displaced rats as the dominant laboratory rodent during the 1990s when mouse-specific genetic knockout and transgenic tools became widely available, but the development of CRISPR-Cas9 gene editing has restored the rat's utility by enabling targeted gene modification without the mouse-centric infrastructure that previously constrained rat genetics.

Physiological and Anatomical Characteristics

The rat cardiovascular system, with a heart rate of 250 to 450 beats per minute and a body weight of 250 to 500 grams in adult animals, supports instrumented studies of hypertension, heart failure, and myocardial infarction that are difficult to replicate in the mouse. Rat metabolic physiology, including hepatic enzyme expression and cytochrome P450 profiles, more closely resembles human drug metabolism than the mouse equivalent, making rats the preferred species for pharmacokinetics studies in early drug development. Research published in ACS Chemical Neuroscience on the comeback of the rat reviews the physiological attributes that distinguish rats from mice and explains why certain pharmacological and surgical endpoints remain achievable only in the larger animal.

Robotics and Computational Modeling

The intersection of rats and engineering extends to robotics and computational neuroscience. Robotic rats have been developed to study social behavior: a biomimetic robot capable of mimicking rat movements and vocalizations can be introduced into a cage as an experimental confederate, producing social interactions that illuminate the neural basis of conspecific recognition and hierarchy formation. Research from PMC on ethorobotic rats for behavioral research describes how such systems enable controlled manipulations of social stimuli that behavioral studies relying on live animal pairs cannot achieve. Computational models of the rat nervous system, calibrated against electrophysiological recordings, are used to develop and test theories of sensorimotor integration, navigation, and decision-making.

Applications

Rats are used as model organisms and research subjects across a wide range of fields, including:

• Neural prosthetics development, including chronic implantable electrode arrays and brain-computer interfaces
• Pharmacological testing and drug metabolism studies in pharmaceutical development
• Cardiovascular disease modeling, including hypertension, heart failure, and ischemia-reperfusion injury
• Behavioral neuroscience, including studies of learning, memory, and addiction
• Toxicology and occupational health exposure assessment