Neurotrophin 4 Infusion for Laryngeal Nerve Regeneration in an Aged Rat

Begin with an anesthetized aged rat, immobilized in a reclined position.

Aging leads to laryngeal muscle denervation and a reduction in neuromuscular junctions—where nerves connect to muscle.

Extend the tongue and insert a plastic speculum to keep the mouth open.

Take an endoscope integrated with a syringe prefilled with neurotrophin-4 (NTF4), a nerve growth factor.

Under dark conditions, turn on the endoscope’s light source.

Initiate video recording and immerse the endoscope tip in warm water to prevent condensation, ensuring a clear field of view.

Using endoscopic guidance, position the needle near the left vocal fold.

As the vocal folds open during inspiration, insert the needle into the left thyroarytenoid muscle, an intrinsic laryngeal muscle.

Deliver the NTF4, then withdraw the needle. Allow the rat to recover.

NTF4 stimulates laryngeal nerve regeneration, which promotes neuromuscular junction formation. This highlights the neurotherapeutic potential of NTF4.

30 minutes before the injection, warm aseptically prepared 50-microliter doses of the neurotrophin or saline in a 25-degree Celsius water bath. When the treatments are ready, recline an anesthetized rat in the supine position on a Plexiglas platform. And use the guidewire to suspend the animal via the top frontal incisors.

Next, attach a 30-gauge 50-millimeter 100-microliter syringe to a 1.9-millimeter 30-degree sinus endoscope. And attach the syringe assembly to a jig on the outer wall of the endoscope. When the syringe is secure, load the treatment. And attach the endoscope assembly to the camera.

Then use rubber-tipped forceps to extend the tongue to the side. And insert a plastic speculum to maintain oral patency. And turn on the halogen light source to the endoscope.

With the video recorder on, immerse the distal end of the endoscope in warm water for a few seconds to minimize the development of condensation on the glass tip. And carefully insert the needle into the area of the left vocal fold, using visual feedback from the monitor as a guide. When the vocal fold is fully visible, inject the needle into the left thyroarytenoid lateral to the white medial edge of the vocal fold. And depress the plunger to deliver the treatment.

If the epiglottis is stuck closed, preventing a clear view of the larynx, use an upward sweeping motion with the syringe tip to gently unstick the tissue.

Then withdraw the needle. And place the animal in its home cage on a heating pad until full recumbency.