Electroacupuncture Reduces Ocular Surface Neuralgia in Dry-Eyed Guinea Pigs by Inhibiting the Trigeminal Ganglion and Spinal Trigeminal Nucleus Caudalis P2X₃R-PKC Signaling Pathway

Abstract

Purpose

To observe the effects of electroacupuncture on ocular surface neuralgia and the P2X₃R-PKC signaling pathway in guinea pigs with dry eye.

Methods

A dry eye guinea pig model was established by subcutaneous injection of scopolamine hydrobromide. Guinea pigs were monitored for body weight, palpebral fissure height, number of blinks, corneal fluorescein staining score, phenol red thread test, and corneal mechanical perception threshold. Histopathological changes and mRNA expression of P2X₃R and protein kinase C in the trigeminal ganglion and spinal trigeminal nucleus caudalis were observed. We performed a second part of the experiment, which involved the P2X₃R-specific antagonist A317491 and the P2X₃R agonist ATP in dry-eyed guinea pigs to further validate the involvement of the P2X₃R-protein kinase C signaling pathway in the regulation of ocular surface neuralgia in dry eye. The number of blinks and corneal mechanical perception threshold were monitored before and 5 min after subconjunctival injection and the protein expression of P2X₃R and protein kinase C was detected in the trigeminal ganglion and spinal trigeminal nucleus caudalis of guinea pigs.

Results

Dry-eyed guinea pigs showed pain-related manifestations and the expression of P2X₃R and protein kinase C in the trigeminal ganglion and spinal trigeminal nucleus caudalis was upregulated. Electroacupuncture reduced pain-related manifestations and inhibited the expression of P2X₃R and protein kinase C in the trigeminal ganglion and spinal trigeminal nucleus caudalis. Subconjunctival injection of A317491 attenuated corneal mechanoreceptive nociceptive sensitization in dry-eyed guinea pigs, while ATP blocked the analgesic effect of electroacupuncture.

Conclusions

Electroacupuncture reduced ocular surface sensory neuralgia in dry-eyed guinea pigs, and the mechanism of action may be associated with the inhibition of the P2X₃R-protein kinase C signaling pathway in the trigeminal ganglion and spinal trigeminal nucleus caudalis by electroacupuncture.

Keywords:

• Electroacupuncture
• dry eye
• ocular surface neuralgiatrigeminal ganglion
• spinal trigeminal nucleus caudalis
• P2X₃R-PKC signaling pathway

Authors’ contributions

WPG designed experiments. TJ, XL, YL, and PCL carried out animal experiments. LS and LJL conducted the statistics. TJ and MMW analyzed the data. TJ drafted the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data used to support the results of this study can be obtained from the corresponding author on reasonable request.

Additional information

Funding

This project was supported by the National Natural Science Foundation of China [No. 82074526, Nanjing, China].