How is castration performed on rats? - briefly
The animal is anesthetized, a ventral midline incision is made to expose the testes, which are then ligated or excised and the wound closed with sutures or tissue adhesive. Post‑operative analgesia is provided and the rat is observed for infection and proper wound healing.
How is castration performed on rats? - in detail
The surgical removal of the testes in laboratory rats follows a standardized protocol to ensure reproducibility and animal welfare.
Pre‑operative preparation
- Acclimate the animal to the procedure area for at least 30 minutes.
- Fast the rat for 2–4 hours to reduce the risk of regurgitation.
- Verify weight (generally 200–300 g) to calculate drug dosages accurately.
Anesthesia and analgesia
- Induce anesthesia with an inhalant agent (e.g., isoflurane 2–3 % in oxygen) delivered via a calibrated vaporizer.
- Maintain a surgical plane of anesthesia, confirmed by the absence of pedal reflex.
- Administer a pre‑emptive analgesic, such as buprenorphine (0.05 mg kg⁻¹, subcutaneously).
Aseptic technique
- Perform hand sterilization and wear sterile gloves.
- Disinfect the ventral abdominal skin with 70 % ethanol followed by povidone‑iodine.
- Drape the surgical field with sterile gauze.
Surgical steps
- Position the rat in dorsal recumbency on a heated surgical platform to maintain body temperature.
- Make a midline skin incision of 1–1.5 cm, extending from the level of the umbilicus to just caudal of the scrotum.
- Incise the underlying musculature (linea alba) using fine scissors or a micro‑scalpel.
- Exteriorize each testis through the incision with a pair of blunt forceps.
- Identify the spermatic cord; isolate it from surrounding tissue.
- Apply a double ligature using 4‑0 absorbable suture (e.g., polyglycolic acid) placed 2 mm distal to the testis.
- Transect the cord between the ligatures with microsurgical scissors.
- Remove the testis, confirming complete excision.
- Inspect the cord stump for bleeding; achieve hemostasis with additional ligatures or cautery if needed.
- Return the remaining tissue to the abdominal cavity.
- Close the muscular layer with a continuous 4‑0 absorbable suture.
- Approximate the skin using wound clips or a simple interrupted 4‑0 non‑absorbable suture.
Post‑operative management
- Place the animal in a recovery cage with a warming pad until normal ambulation resumes.
- Continue analgesia (e.g., buprenorphine every 12 h for 48 h).
- Monitor for signs of infection, dehiscence, or hemorrhage daily for at least 7 days.
- Provide soft bedding and easy access to water and food.
Alternative approaches
- Chemical castration (e.g., GnRH agonists) can be employed when surgical removal is contraindicated, but it requires repeated dosing and monitoring of hormone levels.
- Bilateral orchiectomy via a scrotal approach is possible in larger rodents but offers limited visibility compared to the ventral abdominal method.
Adherence to these steps yields a reproducible, humane procedure that minimizes intra‑operative complications and promotes rapid recovery.