How to open a rat’s mouth? - briefly
Secure the rat by gently gripping its tail base and supporting its body, then place a thumb and forefinger on either side of the lower jaw and apply slight outward pressure to separate the incisors. If required, use a smooth, small instrument to keep the mouth open for examination.
How to open a rat’s mouth? - in detail
Accessing the oral cavity of a laboratory rat requires proper restraint, adequate anesthesia, and appropriate tools to prevent injury to the animal and the handler.
First, prepare a clean work surface and gather the necessary equipment: small animal anesthesia machine or isoflurane vaporizer, a stereomicroscope or magnifying lamp, fine forceps or a calibrated spring‑loaded mouth gag, a soft towel or gauze for wrapping, and a sterile swab for cleaning the teeth. Verify that all instruments are sterilized and that the anesthesia delivery system is functioning correctly.
Second, induce anesthesia using a calibrated concentration of isoflurane (typically 2–3 % in oxygen). Confirm the loss of righting reflex and the absence of pedal withdrawal before proceeding. Maintain a stable plane of anesthesia throughout the procedure by monitoring respiration rate and adjusting the vaporizer as needed.
Third, place the rat on its back on a padded surface. Wrap the body loosely with a gauze towel, leaving the head exposed, to limit movement while avoiding pressure on the thorax. One hand should hold the forelimbs gently; the other hand will manipulate the head.
Fourth, open the mouth using one of the following methods:
- Spring‑loaded gag: Position the gag’s inner jaws behind the incisors, then gently compress the lever to separate the mandible. Release the lever once the mouth is adequately opened.
- Fine forceps: Grasp the maxillary incisors near the base with a pair of fine, smooth‑jawed forceps. Apply steady, slight traction to pull the upper teeth forward while simultaneously supporting the lower jaw with the thumb and index finger. Avoid excessive force that could fracture the teeth.
- Tongue depressor: Insert a sterile, blunt probe between the molars and press downward to keep the mouth open while the incisors are held with forceps.
Maintain the opened position for the required duration, typically no longer than a few minutes, to minimize stress. Use the magnifying lamp to inspect the oral cavity, collect samples, or perform dental procedures as needed.
Finally, discontinue anesthesia and place the rat in a warm recovery cage. Observe the animal until normal grooming and locomotion resume. Record the procedure details, including anesthetic concentration, duration of mouth opening, and any complications, in the laboratory log.
Adhering to these steps ensures safe and effective access to the rat’s oral cavity while upholding ethical standards and animal welfare.