Where is saline administered to a rat? - briefly
Saline is typically injected into the rat’s peritoneal cavity or into the subcutaneous tissue of the dorsal flank. These sites ensure rapid absorption and minimal stress for the animal.
Where is saline administered to a rat? - in detail
Saline solution is typically introduced into a rat through one of several well‑established anatomical sites, each chosen according to experimental objectives, volume requirements, and animal welfare considerations. The most common locations are:
- Intraperitoneal cavity (IP). A small‑gauge needle (27–30 G) is inserted at a 30‑45° angle into the lower right quadrant of the abdomen, avoiding the liver and intestines. This route permits rapid systemic distribution for volumes up to 5 ml kg⁻¹.
- Subcutaneous tissue (SC). The needle is placed in the dorsal neck or flank region, creating a shallow pocket under the skin. Volumes of 1–2 ml kg⁻¹ are well tolerated, providing slower absorption than IP.
- Intravenous access (IV). The lateral tail vein is cannulated with a 25–27 G catheter, allowing precise delivery of small volumes (0.1–0.5 ml kg⁻¹) for rapid plasma equilibration.
- Intracerebroventricular (ICV). A stereotaxic apparatus guides a fine needle (30–33 G) to the lateral ventricle, delivering microliter‑scale volumes (2–5 µl) for central nervous system studies.
- Intramuscular injection (IM). The quadriceps or hindlimb muscle is selected, using a 25–27 G needle to deposit 0.2–0.5 ml kg⁻¹, suitable for depot‑type administration.
Key procedural elements include:
- Sterile preparation of isotonic saline (0.9 % NaCl) at physiological temperature (≈ 37 °C) to prevent hypothermia.
- Verification of needle placement by gentle aspiration before injection to avoid inadvertent organ puncture.
- Controlled injection rate (≤ 1 ml s⁻¹ for IP, slower for SC and IM) to minimize tissue trauma.
- Post‑injection monitoring for signs of distress, hemorrhage, or abnormal behavior.
Selection of the injection site depends on the pharmacokinetic profile desired, the compound’s physicochemical properties, and the experimental timeline. Proper technique ensures reproducibility and animal welfare while delivering saline accurately to the intended compartment.