Focal demyelination in the pontine trigeminal tracts induces trigeminal neuralgia-like behaviors in adult rats

Objective To investigate whether focal demyelination in the pontine trigeminal tracts (PTTs) can induce trigeminal neuralgia-like behaviors in adult rats. Methods Brain stereotaxic microinjection technology was used to inject 1% lysophosphatidylcholine (LPC) or 1× PBS into the PTT region of male SD rats (weighing 250~270 g) to establish the PTT demyelination model group (LPC group) and control group, respectively. Myelin fluorescent staining was employed to evaluate the demyelination changes in the PTT region. Behavioral experiments were performed to measure the mechanical stimulation threshold of head withdraw response, unilateral eyelid contraction duration and numbers of fast face stroking in rats. Intraperitoneal injection of 50 mg/kg carbamazepine was given to the rats to evaluate their behavioral changes. Results A stable local demyelination model of PTT in adult rats was successfully established by, with the coordinate origin at Bregma, descending glass microelectrode for 9.22 mm with a left-side 18° tilt path from axterior-posterior (AP) -9.86 mm, medial-lateral (ML) 0 mm and dorsal-ventral (DV) 0 mm, and then 250 nL 1%LPC was injected at a rate of 250 nL/min. Myelin fluorescent staining demonstrated that the peak of demyelination was observed at the 7th day after modeling. Behavioral experiments showed that compared with the control group, the air-puff gas stimulation threshold and von Frey filament stimulation threshold that triggered the head withdraw response were significantly reduced in the LPC group (P < 0.01). At the 7th day after modeling, there were significant increases in the unilateral eyelid contraction duration and the numbers of unilateral fast face stroking only in the adult rats from the LPC groups (P < 0.01). Carbamazepine significantly decreased the numbers of unilateral fast face stroking evoked by mechanical stimulation (P < 0.01). Conclusion Focal demyelination in the PTTs can induce trigeminal neuralgia-like behaviors in adult rats.