How do you administer a suspension to a rat? - briefly
Inject the prepared suspension intraperitoneally with a sterile 1‑ml syringe fitted with a 25‑gauge needle, delivering the calculated dose in a volume of 1–2 ml per 100 g of body weight. Restrain the rat gently, shave and disinfect the injection site, and insert the needle at a 45° angle to avoid organ injury.
How do you administer a suspension to a rat? - in detail
Delivering a liquid suspension to a laboratory rat requires precise preparation, accurate dosing, and careful technique to ensure reproducibility and animal welfare.
First, formulate the suspension under sterile conditions. Use a vehicle compatible with the test compound—commonly a mixture of sterile water, saline, or a buffered solution with a suitable emulsifier (e.g., Tween 80). Homogenize the preparation with a vortex mixer or sonicator until particles remain uniformly dispersed. Verify concentration by analytical assay and filter through a 0.22 µm membrane if sterility is required.
Second, calculate the dose. Determine the animal’s body weight (in grams) and apply the desired mg kg⁻¹ dosage:
- Dose (mg) = (desired mg kg⁻¹) × (body weight g / 1000)
- Volume (µL) = (dose mg) / (concentration mg mL⁻¹) × 1000
Record the exact volume for each subject to avoid dosing errors.
Third, select the administration route. Common options include:
- Oral gavage: use a stainless‑steel feeding needle (size 20–22 G) with a rounded tip. Insert gently along the palate, advance until resistance is felt, then deliver the calculated volume slowly (≤0.2 mL per 200 g rat). Observe for regurgitation.
- Intraperitoneal injection: employ a 25–27 G needle. Locate the lower right quadrant of the abdomen, insert at a shallow angle (≈30°), and inject the suspension steadily (≤0.5 mL per 200 g rat). Avoid puncturing organs.
- Subcutaneous injection: choose a 25–27 G needle, lift a fold of skin on the dorsal neck region, insert bevel up, and deposit the suspension (≤0.2 mL per 200 g rat). Ensure the fluid forms a visible bleb.
Fourth, restrain the rat using a calibrated restrainer or manual grip, minimizing stress. Apply a brief, gentle tail pinch or use a soft cloth to hold the animal securely. Verify that the animal is alert and breathing normally before proceeding.
Fifth, administer the suspension according to the chosen route. Deliver the volume at a controlled rate to prevent tissue damage or aspiration. After injection, withdraw the needle smoothly and apply gentle pressure with a sterile gauze to the site.
Sixth, monitor the animal for at least 30 minutes post‑dose. Record signs of distress, abnormal behavior, or injection site reactions. Provide access to food and water, and return the rat to its home cage only after recovery of normal activity.
Finally, document all parameters: compound identity, batch number, concentration, calculated dose, injection route, needle gauge, volume delivered, and any observations. Store records in compliance with institutional animal care guidelines and Good Laboratory Practice standards.