Analgesic effect of curcumin on trigeminal neuralgia in rats

Abstract

Objective To evaluate the analgesic effect of curcumin on trigeminal neuralgia in rats. Methods Thirty healthy adult male Sprague-Dawley rats, weighing 200-250 g, aged 7-8 weeks, were divided into 3 groups (n=10 each) using a random number table: sham operation group (group S), trigeminal neuralgia group (group TN) and trigeminal neuralgia + curcumin group (group Cur). Trigeminal neuralgia model was established by injecting cobra venom solution into the sheath of the infraorbital nerve (ION). Starting from 15 days after establishment of the model, curcumin 45 mg/kg was intragastrically administered twice a day for 28 consecutive days in group Cur, while the equal volume of peanut oil was administered in group TN.Before establishment of the model (baseline), and on 4, 7, 14, 21, 28, 35 and 42 days after establishment of the model, the mechanical pain threshold was measured, the free behaviors were observed, and the time and frequency of face-grooming and exploratory behaviors were recorded.After observation of the free behaviors, the ION and medulla oblongata on the affected side were removed for examination of the ultrastructure using transmission electron microscopy. Results Compared with group S, the mechanical pain threshold was significantly decreased, the time of face-grooming behaviors was significantly prolonged, the frequency of face-grooming behaviors was significantly increased, the time of exploratory behaviors was significantly shortened, and the frequency of exploratory behaviors was significantly decreased on 4-42 days after establishment of the model in group TN (P<0.05 or 0.01). Compared with group TN, the mechanical pain threshold was significantly increased, and the time of face-grooming behaviors was significantly shortened on 28-42 days after establishment of the model, and the frequency of face-grooming behaviors was significantly decreased, the time of exploratory behaviors was significantly prolonged, and the frequency of exploratory behaviors was significantly increased on 21-42 days after establishment of the model in group Cur (P<0.05 or 0.01). Microscopic examination revealed that the changes in demyelination of the ION and medulla oblongata were significantly attenuated in group Cur as compared with group TN. Conclusion Intragastrically administered curcumin 45 mg/kg (twice a day for 28 consecutive days) can attenuate trigeminal neuralgia in rats, and the mechanism is related to the attenuated changes in demyelination of the ION and medulla oblongata. Key words: Curcumin; Trigeminal neuralgia; Analgesic