ProtocolPeripheral targeting of the trigeminal ganglion via the infraorbital foramen as a therapeutic strategy
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.
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Inflammation-induced changes in primary afferent-evoked release of substance P within trigeminal ganglia in vivo
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