What is the normal body temperature of rats? - briefly
The typical core temperature of a laboratory rat ranges from about 37 °C to 38 °C (98.6–100.4 °F). Minor variations occur with strain, age, and environmental conditions.
What is the normal body temperature of rats? - in detail
Rats maintain a core temperature that generally falls between 38.0 °C and 39.5 °C (100.4 °F–103.1 °F) under standard laboratory conditions. This range represents the physiological set point for adult, healthy specimens of common strains such as Sprague‑Dawley, Wistar, and Long‑Evans.
Measurement of this parameter is most reliable with rectal thermometers or implanted telemetry devices. Rectal probes provide instantaneous readings with an accuracy of ±0.2 °C when inserted 2–3 cm beyond the anal verge. Telemetry implants, positioned in the peritoneal cavity or subcutaneously, deliver continuous data and minimize handling stress.
Several variables shift the observed temperature:
- Strain differences: Certain inbred lines exhibit slightly higher baselines (up to 39.8 °C) compared to outbred stocks.
- Age: Neonates display lower core values (≈ 36.5 °C), rising to adult levels by post‑natal day 21.
- Sex: Females may run 0.2 °C lower on average during estrus cycles.
- Ambient temperature: Housing at 22 °C induces mild thermoregulatory effort; temperatures above 27 °C can raise core values by 0.5 °C.
- Circadian rhythm: Peak temperatures occur during the dark phase (active period), typically 0.3 °C above daytime minima.
- Stress and anesthesia: Acute handling elevates temperature transiently; inhalational anesthetics such as isoflurane depress core temperature by 1–2 °C.
Thermoregulatory mechanisms in rats involve brown adipose tissue activation, vasomotor adjustments, and behavioral responses (e.g., nesting). Disruption of these processes—through pharmacological agents, disease models, or environmental extremes—manifests as deviations from the 38.0–39.5 °C window.
Accurate monitoring is essential for experimental reproducibility, especially in studies of metabolism, neurophysiology, and drug pharmacokinetics, where temperature fluctuations can alter biochemical rates and behavioral outcomes.