Elsevier

Brain Research Protocols

Volume 15, Issue 3, September 2005, Pages 119-126
Brain Research Protocols

Protocol
Peripheral targeting of the trigeminal ganglion via the infraorbital foramen as a therapeutic strategy

https://doi.org/10.1016/j.brainresprot.2005.05.003Get rights and content

Abstract

A unique interventional approach for modulating sensory signaling involves targeting neurons in the sensory ganglia through use of pharmacological or gene therapies. This has previously been accomplished in the trigeminal system via stereotactic ganglionic microinjections. However, this procedure can be time consuming and requires expensive stereotactic equipment. The current paper describes a percutaneous approach for injecting the trigeminal ganglion with an electrical-stimulation needle inserted through the infraorbital foramen, infraorbital canal and foramen rotundum. The needle tip was positioned in the ganglion by eliciting a twitch in the ipsilateral masseter following electrical stimulation. The technique was imaged using computerized tomography and methylene blue dye to verify the site of the injection. We validated this technique by reproducing the results from our prior study that involved injection of resiniferatoxin (RTX) into the trigeminal ganglion using the stereotactic approach. Both techniques for intraganglionic injection of RTX produced a specific deletion of C-fiber neurons, as demonstrated by inhibition of neurogenic-induced plasma extravasation and behavioral assays. Thus, we propose a novel and simple technique for studying mechanisms of peripheral sensory modulation of orofacial pain via direct application of drugs, tracers or viral vectors around trigeminal sensory neuronal cell bodies. This technique minimizes trauma to brain structures that may have an impact on pain perception.

Section snippets

Type of research

  • (i)

    Trigeminal ganglion (TG) as an investigative or therapeutic site [4], [6], [7], [9].

  • (ii)

    Pharmacological pain therapy in rodents.

Time required

The entire procedure can be completed at a rate of 5 animals per hour.

Anesthesia induction: 5 min/animal. Note that multiple animals can be induced concurrently in order to save time.

Shaving: 1 min/animal.

Needle insertion and locating the trigeminal ganglia: <5 min/animal.

Injection: 1 min.

Recovery from anesthesia: <1 h.

Animals

Male Sprague–Dawley rats (Charles River Laboratory, Wilmington, MA), 3 months old, weighing 300–350 g, were housed in bedded bins, with no animal placed in isolation. Food and water were available ad libitum. Animal testing procedures and general handling complied with the ethical guidelines and standards established by the Institutional Animal Care and Use Committee (IACUC) at the University of Florida (UF), and all procedures complied with the Guide for Care and Use of Laboratory Animals [2].

Special equipment

Animal preparation

Male Sprague–Dawley rats (300–350 g) were deeply anesthetized using a ketamine (40–80 mg/kg, i.p.) and xylazine solution (8–10 mg/kg, i.p.). The animals were then shaved with clippers to remove the facial hair covering the infraorbital foramen, and care was taken to not remove any of the whiskers. This region was then wiped with an iodine solution ([Betadine], 10%) to prepare the area. Animals were maintained on a thermal blanket to keep their core temperature at 37 °C.

Trigeminal ganglion injection

Each animal was placed

Verification of a trigeminal ganglion location injection

Methylene blue was injected to visualize that the flow was localized to the TG (Fig. 1A, inset). The dura overlying the TG allowed for the dye to remain within its confines. Examination of the CT-reconstructed images, segmented to show the bony regions, demonstrated that the needle coursed through the infraorbital foramen (IOF) and the foramen rotundum (Fig. 2A).The needle tip terminated near the medial wall of Meckel's cave (Figs. 2B, C). Note that the trigeminal ganglion is enclosed within

Protocol assessment

Precise localized drug delivery strategies for pain control can minimize non-specific effects often seen with systemic routes of administration. Specific application to cell bodies in sensory ganglia provides an ideal target for this approach, as the somata of sensory neurons has been proposed as a unique site for modulation of sensory signaling [3]. Advantages of drug application directly to the sensory ganglia include: (1) accessing a peripheral modulation site, (2) targeting specific sensory

Quick procedure

  • 1.

    Deeply anesthetize animals, shave and sanitize the injection site.

  • 2.

    Palpate the zygomatic process and insert the needle through the infraorbital foramen and guide the needle along the infraorbital canal and then finally through the foramen rotundum.

  • 3.

    Activate the electrical stimulation needle and adjust the needle position until the ipsilateral masseter contracts with each stimulatory electrical pulse. Then, inject the solution slowly into the trigeminal ganglion.

  • 4.

    Observe the animal post-injection

Essential literature references

Original papers: [6], [9]

Acknowledgments

This work was supported by Grant #1K22DE014865-01A1, National Institute of Dental and Craniofacial Research, National Institutes of Health, Department of Health and Human Services, Bethesda, MD, USA.

References (9)

There are more references available in the full text version of this article.

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  • Antinociceptive effect of ultra-low dose naltrexone in a pre-clinical model of postoperative orofacial pain

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    Citation Excerpt :

    At the end of the procedure the animals were kept in a heated room until their complete recovery from anesthesia. The injection into the trigeminal ganglion (TG) was performed according to (Neubert et al., 2005) with minor adaptations (Araya et al., 2017). Animals were briefly anesthetized with 4% halothane in oxygen and placed on a surgical table.

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