(−)-α-Bisabolol reduces nociception and trigeminal central sensitisation in acute orofacial neuropathic pain induced by infraorbital nerve injury

Abstract

Neuropathic orofacial pain conditions represent a challenge to diagnose and treat. Natural substances are promising therapeutic options for the control of pain. AimsThis study aimed to examine whether (−)-α-bisabolol (BISA), a natural terpene, can attenuate nociceptive behaviour and central sensitisation in a rodent model of trigeminal neuropathic pain. Materials and methodsInfraorbital nerve transection (IONX) or sham operation was performed in adult male rats. Head withdrawal thresholds as a measure of facial mechanical sensitivity were tested with von Frey monofilaments applied bilaterally to the facial vibrissal pad pre-operatively (baseline) and then post-operatively before and at 60, 120, 240 and 360 min after administration of vehicle control per oris (p.o.) or BISA (200 mg/kg p.o.) (n = 8/group). Effects of BISA or vehicle on the activity of nociceptive neurons recorded in the medullary dorsal horn (MDH) were tested on post - operative day 8–10. ANOVA followed by post-hoc Bonferroni tested for statistically significant differences (p < 0.05) across study groups and time points. Key findingsIONX animals (but not sham or naïve animals) showed post-operative facial mechanical hypersensitivity that was unaffected by vehicle. However, administration of BISA at post-operative day 7 significantly reversed the mechanical hypersensitivity in IONX rats; this effect lasted for at least 6 h. BISA also attenuated IONX-induced central sensitisation of MDH nociceptive neurons, as reflected in reversal of their reduced activation thresholds, increased responses to graded mechanical stimuli and enhanced spontaneous activity. SignificanceBISA may attenuate nociceptive behaviour and central sensitisation in a rat model of acute trigeminal neuropathic pain.