Question 1

When is intradermal injection used in rodent research?

Accepted Answer

Intradermal injection delivers compounds into the space between the epidermis and dermis layers. This route is typically used to assess inflammation, measure cutaneous blood flow, or evaluate allergenic reactions to antigens. The procedure requires anesthesia and specialized training to ensure accurate placement and minimize tissue damage at the injection site.

Question 2

What are the key advantages of intranasal administration in laboratory animals?

Accepted Answer

Intranasal administration is non-invasive and requires minimal training and simple equipment like a calibrated micropipette. The nasal mucosa's rich blood vessel and nerve supply enables rapid systemic absorption and direct central nervous system targeting. This route is commonly used for vaccine delivery and local decongestant applications in rodents.

Question 3

Why is anesthesia recommended for intranasal dosing in conscious rodents?

Accepted Answer

Anesthesia during intranasal administration ensures proper compound placement at the nares for accurate dosing, prevents animals from biting equipment, and eliminates head jerking that could injure nasal tissue or eyes. Anesthesia also reduces the likelihood of the animal snorting and spraying the compound from the nares upon administration.

Question 4

What volume limits apply to intranasal administration in different rodent species?

Accepted Answer

For rats, intranasal administration should not exceed 50 microliters per administration. For mice, the maximum total volume is less than 20 microliters. These volume restrictions prevent complications and ensure compliance with institutional guidelines and IACUC-approved protocols for safe compound delivery.

Question 5

How is needle depth controlled during neonatal intracranial injection?

Accepted Answer

A needle guard is created by measuring the correct needle against its cap, marking the desired length, and cutting the cap with a razor blade to produce a clean, level cut. This custom depth-control device is prepared aseptically and ensures the needle penetrates only to the validated depth appropriate for the target brain structure and animal age.

Question 6

What preparation steps are essential before intradermal injection in rodents?

Accepted Answer

The injection site must be shaved using an electric razor or depilatory cream, then thoroughly cleaned with water-dampened gauze to remove lingering hair. A topical antiseptic solution is applied to the shaved area. The skin is stabilized by stretching it between thumb and index finger before needle insertion to ensure accurate bleb formation.

Question 7

Why is a separate needle used to draw test articles for intracranial injection?

Accepted Answer

A separate needle is used to draw the test article because insertion into the stopper significantly dulls fine-gauge needles, which compromises injection quality. Using a fresh needle for intracranial administration preserves needle sharpness and ensures precise, trauma-free delivery directly into the neonatal rodent brain.

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