EVALUATION OF MYRTENOL ON MECANICHAL HYPERALGESIA INDUCED BY GP120

Resumo

Introduction: Myrtenol is a monoterpene that can be found in aromatic plants species from several families like the Cyperaceae family, the Rasaceae family, the Myrtaceae family among others1. Studies show that the myrtenol is a potencial pharmacological agent, that can be employed as an anti-inflammatory and antinociceptive, among others1,2,3. Objective: The objective of this study was to evaluate the antihyperalgesic potential of myrtenol in a nociception model induced by gp120. Material and Methods: The animals were divided into the following groups: Control Group (n=7), that received sterile saline solution and Myrtenol Group (n=6), both treated orally. With a Hamilton’s micro- syringe (25 ?L), it was injected via intrathecal, 5?L of gp120 protein between L5 and L6 vertebrae through intact skin. This procedure was made one hour after the oral treatment with Myrtenol (30 mg/kg). After the intrathecal injection, the animals were placed in individual acrylic boxes for one hour for accustoming. The mechanical hyperalgesia was determined by the paw removal threshold using the electronic analgesymeter (InSight®, Ribeirão Preto, Brazil). The measure was realized on the animal’s right back paw, and the pressure was determined in grams, after the paw removal. The analyses were made two and three hours after the gp120 intrathecal injection. The experimental procedures executed in this study were in accordance with the Ethical Principals in Animal Research and approved by the Committee for Ethics in Animal Experimentation at the UFGD (Protocol number 26/2016). Results: Two hours after the gp120 intrathecal injection the control group showed, on average, a paw removal threshold of one gram while the Myrtenol group showed a diferent significative (P <0.05) paw removal threshold of two grams on average. Three hours after the injection, the control group showed a paw removal threshold of 0,7 grams on average, while the Myrtenol group showed 0,9 grams. Discussion and Conclusion: According to a statistic analysis, it can be concluded that the myrtenol solution presents hyperalgesia inhibition up to three hours after the gp120 intrathecal injection. In the second hour the myrtenol solution reverted 100% of the mechanical hyperalgia compared to the control group. In the third hour the myrtenol solution efficacy could still be detected, but was nearly unexpressive.