How should a rat's temperature be measured? - briefly
Use a calibrated rectal probe inserted 1–2 cm into the anus, allowing at least 30 seconds for stabilization, or employ a surgically implanted telemetric device for continuous core temperature monitoring.
How should a rat's temperature be measured? - in detail
Accurate assessment of a rodent’s core temperature requires a method that minimizes stress and yields reproducible data. The most reliable techniques are rectal thermometry, infrared thermography, and implanted telemetry devices; each has specific procedural steps.
Rectal thermometry provides direct measurement of core temperature. Use a lubricated, calibrated digital thermometer with a probe length of 8–10 mm. Restrain the animal gently in a transparent tube or with a soft restrainer, insert the probe 2–3 mm beyond the anal verge, and hold for 10–15 seconds until the reading stabilizes. Record the temperature to the nearest 0.1 °C. Clean the probe with isopropanol between animals to prevent cross‑contamination.
Infrared thermography offers non‑invasive surface temperature estimation. Position a calibrated infrared camera at a fixed distance (15–20 cm) from the animal’s dorsal region. Allow the rat to acclimate in a temperature‑controlled enclosure (22 ± 1 °C) for at least 5 minutes before imaging. Capture multiple frames and calculate the mean of the highest 5 % pixel values to approximate core temperature, acknowledging a typical deviation of ±0.5 °C compared to rectal data.
Implanted telemetry delivers continuous, high‑resolution core temperature recordings. Implant a miniature temperature probe into the peritoneal cavity under general anesthesia (isoflurane 1–2 %). Secure the transmitter subcutaneously, close incisions with absorbable sutures, and allow a 7‑day recovery period. Program the receiver to log temperature at intervals of 5–10 minutes. Verify signal integrity daily and calibrate the system against a known reference thermometer before each experiment.
Key procedural considerations:
- Acclimatization: Maintain a constant ambient temperature and humidity; avoid sudden environmental changes.
- Handling stress: Use gentle restraint or habituation training to reduce sympathetic-induced hyperthermia.
- Calibration: Verify thermometer accuracy weekly with a certified reference standard.
- Data integrity: Document time of day, animal’s activity level, and any anesthetic agents used, as these factors influence thermoregulation.
- Ethical compliance: Follow institutional animal care guidelines, provide analgesia when invasive procedures are performed, and monitor for postoperative complications.
Selecting the appropriate method depends on experimental goals: single-point measurements favor rectal probes; longitudinal studies benefit from telemetry; and rapid screening may rely on infrared imaging. Consistent technique, proper calibration, and controlled environmental conditions ensure reliable temperature data in rodent research.