Resumen de Antinociceptive Effects of Mirtazapine, Pregabalin, and Gabapentin After Chronic Constriction Injury of the Infraorbital Nerve in Rats
Kunihiro Nakai, Aya Nakae, Ryota Hashimoto, Takashi Mashimo, F. Hosokawa, Ko Hosokawa
Aims: To clarify the antiallodynic effects of the ?2-adrenergic receptor antagonist mirtazapine compared with those of gabapentin and pregabalin in a rat model of orofacial neuropathic pain. Methods: Mirtazapine (10, 30, and 100 ?g), gabapentin (10, 30, and 100 ?g), and pregabalin (3, 10, and 30 ?g) were administered intrathecally to eight male Sprague-Dawley rats with orofacial neuropathic pain induced by chronic constriction injury of the infraorbital nerve that had been carried out 2 weeks previously. Stimulation using von Frey filaments (1.0 to 15.0 g) applied to skin innervated by the injured infraorbital nerve enabled the measurement of mechanical thresholds 0 to 180 minutes after drug injection. Time-course data for the dose-response effects were analyzed using two-way analysis of variance and the posthoc Tukey-Kramer multiple-comparison test.
Results: Intrathecal administration of not only gabapentin and pregabalin but also mirtazapine reversed the lowered mechanical nociceptive thresholds produced by the nerve injury. The ED50 (95% confidence interval) was (in ?g) 49.00 (39.71-58.29) for mirtazapine, 54.84 (46.12-63.56) for gabapentin, and 13.47 (11.24-15.69) for pregabalin.
Conclusion: Intraspinal administration of either mirtazapine, gabapentin, or pregabalin reverses the lowered facial mechanical thresholds produced in a rat model of trigeminal neuropathic pain.
