How to induce labor in a rat? - briefly
Labor can be initiated in pregnant rats by injecting a prostaglandin F₂α analog (e.g., cloprostenol) or by administering oxytocin at 0.5–1 IU per animal. Mifepristone (RU‑486) at 2 mg/kg also induces parturition by antagonizing progesterone receptors.
How to induce labor in a rat? - in detail
Inducing parturition in laboratory rats requires strict adherence to ethical standards, precise dosing, and careful monitoring. The procedure begins with approval from an institutional animal care committee, ensuring compliance with national regulations for humane treatment.
Select healthy, timed‑pregnant females (gestational day 21–22). Confirm pregnancy by palpation or ultrasound. Maintain animals in a controlled environment (temperature 22 ± 2 °C, 12 h light/dark cycle) with ad libitum access to food and water.
Pharmacological agents
- Prostaglandin F₂α (PGF₂α): Commonly used to trigger uterine contractions. Prepare a sterile solution (e.g., 0.1 mg ml⁻¹ in saline). Administer 0.1–0.2 mg/kg subcutaneously. Observe for signs of labor within 30–90 min.
- Oxytocin: Augments uterine contractility after PGF₂α. Dilute to 1 IU ml⁻¹ in sterile saline. Deliver 0.5–1 IU intravenously or intraperitoneally, repeat every 10 min if necessary, not exceeding 5 IU total.
- Mifepristone (RU‑486): Antagonizes progesterone, facilitating cervical ripening. Dissolve 10 mg ml⁻¹ in a vehicle of 10 % ethanol, 90 % saline. Inject 10 mg kg⁻¹ subcutaneously 24 h before PGF₂α. This step reduces the required prostaglandin dose.
Procedure
- Baseline assessment – Record body weight, temperature, and respiratory rate. Ensure no signs of distress.
- Hormone administration – Follow the chosen regimen (PGF₂α alone, or combined with oxytocin/mifepristone). Use sterile syringes and needles appropriate for the animal’s size.
- Observation – Place the rat in a quiet, temperature‑controlled cage. Monitor for abdominal contractions, nesting behavior, and expulsion of pups. Document the interval from injection to first pup delivery.
- Support – If contractions are weak, administer an additional oxytocin bolus (0.5 IU). Provide warm bedding to prevent hypothermia in neonates.
- Post‑delivery care – Verify that all pups are alive and nursing. Return the dam to its home cage after a 30‑min recovery period. Record litter size, birth weights, and any abnormalities.
Safety considerations
- Use personal protective equipment when handling hormones.
- Dispose of waste according to hazardous material guidelines.
- Monitor for adverse reactions such as excessive bleeding, uterine rupture, or maternal distress. Terminate the protocol if severe complications arise.
Data reporting
Report gestational day, strain, dosing schedule, route of administration, latency to delivery, litter outcomes, and any deviations from the protocol. Include statistical analysis when comparing different induction methods.
By following these steps, researchers can reliably initiate parturition in rats while minimizing animal stress and ensuring reproducible results.