How can you freeze mice and rats? - briefly
Place the rodents in a sealed, sterile container and store it in a -20 °C (or colder) freezer for a minimum of 24 hours to ensure complete freezing.
How can you freeze mice and rats? - in detail
Freezing small rodents is a procedure employed in laboratory preservation, genetic resource banking, and controlled pest‑management programs. Execution requires compliance with institutional animal‑care regulations, appropriate equipment, and a defined protocol to maintain tissue integrity and avoid undue suffering.
Prior to temperature reduction, rodents must be euthanized using an approved method such as CO₂ inhalation, overdose of anesthetic agents, or cervical dislocation performed by a trained technician. Immediate placement of the carcass into a pre‑cooled container prevents post‑mortem degradation.
Equipment commonly used includes:
- Ultra‑low‑temperature freezer set to –80 °C or lower
- Liquid‑nitrogen dewar (–196 °C) for rapid cryogenic freezing
- Cryovials or sealed, airtight tubes compatible with the chosen storage temperature
- Temperature data logger to verify stable conditions
Step‑by‑step protocol:
- Label each cryovial with species, strain, sex, date, and identification number.
- Place the euthanized animal into a sterile, pre‑chilled container (e.g., aluminum foil pouch) to reduce thermal shock.
- Transfer the container to the ultra‑low‑temperature freezer; allow a gradual temperature drop of approximately 1 °C per minute to minimize ice crystal formation.
- For rapid preservation, immerse the sealed cryovial in liquid nitrogen for 5–10 minutes, then move it to the –80 °C freezer for long‑term storage.
- Record the exact time of freezing and the temperature reached in the logbook or electronic system.
After freezing, maintain a consistent –80 °C environment or store vials in liquid‑nitrogen tanks for indefinite periods. When retrieval is required, thaw the specimen in a 37 °C water bath until the ice fully melts, then proceed with downstream applications such as DNA extraction, histology, or reanimation protocols that demand viable tissue.
Safety measures include wearing cryogenic gloves, face shield, and lab coat; ensuring adequate ventilation when using liquid nitrogen; and regularly inspecting storage units for temperature excursions. Documentation of each step satisfies audit requirements and supports reproducibility across experiments or operational cycles.