Where should prednisolone be injected in a rat? - briefly
Prednisolone is most commonly delivered to rats by an intraperitoneal injection, placing the drug into the peritoneal cavity for rapid systemic absorption. A subcutaneous injection in the dorsal neck region may be used when a slower release profile is required.
Where should prednisolone be injected in a rat? - in detail
The drug prednisolone is commonly administered to laboratory rats via routes that provide reliable absorption while minimizing stress and tissue damage. The most frequently used sites are intraperitoneal (IP), subcutaneous (SC), and intramuscular (IM). Each route has specific technical requirements.
Intraperitoneal injection
- Needle: 25‑27 G, ½ in. length.
- Injection point: lower right quadrant of the abdomen, midway between the midline and the flank, avoiding the liver and intestines.
- Volume: ≤ 2 mL/kg body weight.
- Technique: bevel up, needle inserted at a shallow angle (≈ 20°) to the skin, aspirate to confirm entry into the peritoneal cavity, then inject slowly.
Subcutaneous injection
- Needle: 25‑27 G, ⅝ in. length.
- Injection point: loose skin over the dorsal thoracic region or the scruff (nape) of the neck.
- Volume: ≤ 0.5 mL per site; larger volumes may be split across multiple sites.
- Technique: pinch the skin to create a tent, insert needle bevel up at a 45° angle, inject steadily, release the skin after needle withdrawal.
Intramuscular injection
- Needle: 23‑25 G, 1 in. length.
- Injection point: quadriceps femoris (mid‑thigh) or the gluteal muscle.
- Volume: ≤ 0.2 mL per site to avoid excessive pressure.
- Technique: locate the muscle bulk, insert needle perpendicular to the skin, aspirate to rule out blood entry, inject slowly, withdraw needle and apply gentle pressure.
Intravenous injection
- Needle: 26‑30 G, ½ in. catheter or tail vein cannulation.
- Injection point: lateral tail vein.
- Volume: ≤ 0.1 mL, diluted in sterile saline if needed.
- Technique: warm the tail to dilate vessels, use a catheter for repeated dosing; ensure flush with heparinized saline to maintain patency.
Selection of the route depends on experimental goals. IP delivers rapid systemic exposure with moderate absorption variability. SC provides slower, sustained release, useful for chronic dosing. IM yields intermediate absorption and is suitable when larger volumes are required. IV offers immediate plasma concentrations but demands technical skill and carries higher risk of vascular injury.
Regardless of the chosen site, maintain aseptic conditions: use sterile syringes, disinfect the injection area with 70 % ethanol, and dispose of sharps in approved containers. Record the exact site, volume, needle gauge, and any observed adverse reactions for reproducibility and animal welfare compliance.