Oral gavage is a technique used in scientific research to administer substances directly into the stomach of an animal, commonly mice. This method ensures a precise, controlled dose of liquid or suspension reaches the digestive system, bypassing the oral cavity and preventing the animal from altering its intake. Researchers employ oral gavage to consistently deliver compounds for various studies, allowing reliable data collection on absorption, metabolism, and effects.
Understanding Oral Gavage
Oral gavage delivers a specific volume of a substance directly into an animal’s gastrointestinal tract, typically the stomach. This technique is favored over other oral administration methods, such as mixing substances into food or drinking water, because it eliminates variability in intake among individual animals. It ensures each animal receives the exact intended amount, which is important for studies requiring accurate dosage control.
The method allows researchers to administer precise doses of various liquids or suspensions, including drugs, nutrients, or microbial solutions. This direct delivery ensures the substance enters the digestive system as intended, which is beneficial for studying its effects on the gut or systemic absorption. While it is a common and generally safe procedure when performed correctly, it is more invasive than simply providing substances in food or water, requiring careful handling of the animal.
How the Procedure is Performed
Oral gavage on mice requires specialized equipment and a skilled hand for a safe and effective procedure. The primary tool is a gavage needle or feeding tube, which is typically a thin, flexible or rigid tube with a rounded, bulb-like, or pear-shaped tip to prevent injury to the esophagus and other tissues. These needles come in various gauges and lengths for different animal sizes.
The process begins with weighing the mouse to determine the appropriate dosing volume, which should not exceed 1% (10 mL/kg) of the animal’s body weight, for example, 0.2 mL for a 20g mouse. The gavage needle’s length is then measured from the animal’s nose to the sternum or last rib, marking the tube to prevent stomach perforation.
Next, the mouse is carefully restrained, typically by scruffing the skin over its shoulders, which immobilizes the head and extends the neck to create a straight line through the esophagus. The gavage tube is then gently inserted into the side of the mouth, behind the incisors, and advanced along the upper palate towards the back of the throat. The tube should pass easily into the esophagus, and the animal may exhibit a swallowing reflex as it is advanced.
If any resistance is felt, the tube should be withdrawn and the attempt repeated. Once the needle is properly positioned, the substance is slowly injected from a syringe attached to the tube, avoiding rotation of the tube to prevent esophageal rupture. After administration, the tube is gently removed along the same insertion angle, and the animal is monitored for a short period for any signs of distress.
Key Research Applications
Oral gavage is used across various scientific disciplines for its ability to deliver precise and controlled doses of substances.
Pharmacology
In pharmacology, it is a routine method for drug development and testing. Researchers study pharmacokinetics—how drugs are absorbed, distributed, metabolized, and excreted—and assess drug efficacy. Studies might involve administering new drug candidates to mice via gavage to observe their effects on specific diseases or conditions.
Nutritional Science
In nutritional science, oral gavage facilitates dietary interventions, allowing scientists to administer specific nutrients, supplements, or even entire liquid diets to mice. This controlled delivery helps in understanding the impact of various dietary components on metabolism, health outcomes, and specific physiological processes. Studies might involve supplementing mice with specific bacterial strains to assess their impact on aging, cognitive function, and oxidative stress.
Microbiology
The technique is also extensively employed in microbiology, especially for gut microbiome research. Researchers can administer probiotics, prebiotics, or specific bacterial pathogens directly into the gut, enabling detailed studies on how these microorganisms interact with the host and influence gut health or disease development. For example, human microbiota can be stably engrafted into mice via gavage. Studies have also investigated how oral gavage of nanoparticles can alter gut microbiota composition, providing insights into potential adverse health effects.
Prioritizing Animal Welfare
Ensuring the well-being of mice during oral gavage is a high priority in scientific research, guided by strict ethical considerations and regulatory oversight. Researchers undergo specialized training to become proficient in animal handling and gavage techniques, which helps minimize stress and discomfort for the animals. This training often covers proper restraint methods, accurate tube insertion, and recognition of signs of distress.
Institutions adhere to guidelines set by bodies such as Institutional Animal Care and Use Committees (IACUCs) and national regulations, which mandate humane treatment and protocol design. Animals are closely monitored immediately after the procedure for signs of labored breathing, distress, or complications like aspiration or esophageal trauma. If severe distress or injury occurs, protocols often dictate immediate removal of the tube and, if necessary, euthanasia.