A method to perform direct transcutaneous intrathecal injection in rats

Area of Science:

• Neuroscience
• Pharmacology
• Surgical Techniques

Background:

• Intrathecal (i.t.) drug delivery is crucial for studying central nervous system effects.
• Existing methods often require spinal catheters, which can be invasive and technically demanding.
• A simpler, reliable method for i.t. administration in animal models is needed.

Purpose of the Study:

• To describe and validate a novel, catheter-free direct intrathecal injection technique in rats.
• To assess the ease of use, reproducibility, and safety of the described method.
• To confirm the method's utility in pain research by validating known pharmacological effects.

Main Methods:

• Direct intrathecal injections were performed in awake rats without a spinal catheter.
• Injection success was confirmed by an observable tail-flick response.
• Methylene blue was used to visualize injection localization and diffusion.
• The method was validated using morphine for antinociception and naloxone to block systemic morphine effects in a mononeuropathic rat model.

Main Results:

• The direct intrathecal injection technique was easily performed in awake animals.
• The method yielded rapid and reproducible results without observable motor impairment.
• Methylene blue injections showed good localization with minimal diffusion along the spinal cord.
• Intrathecal morphine produced significant antinociception, and intrathecal naloxone effectively blocked systemic morphine's analgesic effect.

Conclusions:

• This catheter-free direct intrathecal injection method offers a simple, safe, and effective approach for drug delivery in rats.
• The technique is suitable for pain research and other studies requiring precise central nervous system administration.
• This method provides a valuable alternative to catheter-based delivery, simplifying experimental procedures.