An Improved Rodent Model of Trigeminal Neuropathic Pain by Unilateral Chronic Constriction Injury of Distal Infraorbital Nerve (dIoN-CCI)

Abstract

The number of studies on trigeminal nerve injury using animal models remains limited. A rodent model of trigeminal neuropathic pain was first developed in the 1994, in which chronic constriction injury is induced by ligation of the infraorbital nerve (IoN-CCI). This animal model has served as a major tool to study trigeminal neuropathic pain. Unfortunately, the surgical procedure in this model is complicated and far more difficult than ligation of peripheral nerves (e.g. sciatic nerve). The aim of this study was to improve on the current surgical procedure of IoN ligation to induce trigeminal neuropathic pain in rats. We demonstrate that the IoN can be readily accessed through a small facial incision. Chronic constriction injury can be induced by ligation of a segment at the distal infraorbital nerve (dIoN-CCI). This dIoN-CCI procedure is simple, minimally invasive and time-saving. Our data show that the dIoN-CCI procedure consistently induced both acute and chronic nociceptive behaviors in rats. Daily gabapentin treatment attenuated mechanical allodynia and reduced face-grooming episodes in dIoN-CCI rats.

Perspective

The orofacial pain caused by trigeminal nerve damage is severe and perhaps more debilitating than other types of neuropathic pain. However, studies on trigeminal neuropathic pain remain limited. This is largely due to the lack of proper animal models given the complexity of the existing surgical procedure required to induce trigeminal nerve injury. Our improved dIoN-CCI model is likely to make it more accessible to study the cellular and molecular mechanisms of neuropathic pain caused by trigeminal nerve damage.