How to stimulate labor in a rat? - briefly
Induce parturition in rats by injecting a prostaglandin F₂α analog (e.g., cloprostenol, 0.1 mg/kg subcutaneously) or a single dose of mifepristone (0.2 mg/kg intraperitoneally), which usually triggers delivery within 12–24 hours. Monitor the animals for labor signs and provide supportive care as needed.
How to stimulate labor in a rat? - in detail
Inducing parturition in laboratory rats requires precise control of physiological cues that naturally trigger delivery. Successful protocols combine hormonal manipulation, pharmacological agents, and careful monitoring of maternal condition.
The most widely adopted approach uses a combination of progesterone withdrawal and oxytocin administration. Progesterone maintains uterine quiescence; its abrupt reduction permits contractions. A typical regimen involves:
- Progesterone withdrawal – on gestation day 21 (rats deliver around day 22), inject 100 µg of mifepristone (RU‑486) subcutaneously. This antagonist blocks progesterone receptors and initiates cervical ripening.
- Oxytocin stimulation – 12 hours after mifepristone, deliver oxytocin intravenously at 0.5 IU/kg. Increase the dose incrementally (0.5–2 IU/kg) until regular uterine activity is observed.
- Supportive fluids – administer isotonic saline (10 ml/kg) intraperitoneally to prevent hypovolemia during strong contractions.
Alternative pharmacological agents include prostaglandin analogs such as cloprostenol (0.1 mg/kg, subcutaneous) or dinoprost (0.5 µg/kg, intramuscular). These compounds directly stimulate myometrial contractility and can be used when oxytocin response is insufficient. Dosage must be titrated to avoid uterine hyperstimulation, which can compromise fetal oxygenation.
Mechanical methods are less common but may be employed in specific research contexts. Cervical dilation using a calibrated Foley catheter (2 mm balloon) for 30 minutes can facilitate passage of pups when cervical remodeling is delayed. This technique requires anesthesia (isoflurane 1–2%) and continuous temperature control.
Monitoring parameters are essential throughout the induction process:
- Body temperature – maintain 37 °C with a heating pad; hypothermia impairs uterine contractility.
- Heart rate and respiration – use a pulse oximeter to detect maternal distress.
- Uterine activity – insert a pressure transducer catheter into the uterine lumen to record contraction frequency and amplitude.
- Fetal viability – assess pup movement and heart rate via ultrasound before and after induction.
Ethical compliance mandates that all procedures follow institutional animal care guidelines. Analgesia (e.g., buprenorphine 0.05 mg/kg, subcutaneous) should be provided post‑delivery to alleviate pain. Researchers must record all interventions, dosages, and outcomes to ensure reproducibility and to facilitate refinement of protocols.
In summary, a reliable induction protocol combines progesterone antagonism, oxytocin or prostaglandin administration, supportive fluid therapy, and rigorous physiological monitoring. Adjustments to dosage and timing should be guided by strain‑specific gestational length, maternal health status, and experimental objectives.