How and with what to give injections to a rat? - briefly
Use a sterile, calibrated syringe equipped with a 27–30 G needle, choose the appropriate route (intraperitoneal, subcutaneous, or tail‑vein), and limit the volume to ≤0.2 ml per 10 g of body weight; gently restrain the rat and, when required, apply brief anesthesia to reduce stress.
How and with what to give injections to a rat? - in detail
Injecting laboratory rats requires precise technique, appropriate equipment, and strict aseptic practice. Select the route based on experimental goals: intraperitoneal (IP) for rapid systemic absorption, subcutaneous (SC) for slow release, intramuscular (IM) for depot delivery, or intravenous (IV) for immediate circulation.
Equipment
- Sterile disposable syringes: 1 mL for volumes ≤0.2 mL, 0.5 mL for ≤0.1 mL.
- Needles: 27–30 G for IP and SC, 25–27 G for IM, 30–33 G for tail vein IV.
- Needle length: ½ in. for SC, ¾–1 in. for IP, ½ in. for IM (hindlimb), ½ in. for tail vein.
- Alcohol swabs, sterile gauze, and a warming pad for tail vein dilation.
Preparation
- Calculate dose in mg/kg, convert to microliters using solution concentration.
- Verify that injection volume does not exceed 10 µL per gram of body weight for IP and SC, 0.1 mL per gram for IM, and 0.2 mL per gram for IV.
- Draw the exact volume, expel air bubbles, and cap the needle.
Restraint and Site Identification
- Use a gentle scruff hold or a restraining tube for IP and SC injections.
- For IM, extend the hindlimb and locate the quadriceps muscle.
- For IV, heat the tail for 1–2 minutes, locate a visible vein, and apply a slight tail stretch.
Administration
- IP: Insert needle at a 30–45° angle into the lower right quadrant of the abdomen, avoiding organs. Aspirate gently; absence of blood confirms correct placement. Depress plunger slowly.
- SC: Pinch a fold of skin on the dorsal neck or flank, insert needle at a 45° angle, and inject steadily.
- IM: Insert needle perpendicularly into the muscle, aspirate to confirm no blood, then deliver the dose.
- IV: Insert needle bevel up into the tail vein, confirm flashback, then inject over 5–10 seconds.
Post‑Injection Care
- Observe the animal for at least 5 minutes for signs of distress, bleeding, or injection site reactions.
- Apply gentle pressure to any bleeding point with sterile gauze.
- Record injection details: route, volume, needle gauge, and batch number of the compound.
Adhering to these steps ensures accurate dosing, minimizes animal discomfort, and maintains experimental integrity.