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Francisco Pellicer,1 Juan M Ortega-Legaspi,2 Rodrigo Martín,3 Sergio Solís-Nájera,4 Lucía Magis-Weinberg,5 Martha León-Olea,6 Ariel Graff-Guerrero,7,8 Camilo de la Fuente-Sandoval,9 Alfredo O Rodriguez3 1Laboratorio de Neurofisiología Integrativa, Dirección de Investigaciones en Neurociencias, Instituto Nacional de Psiquiatría Ramón de la Fuente Muñiz, CDMX, México; 2Department of Medicine, Division of Cardiovascular Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA; 3Departamento de Ingeniería Eléctrica, Universidad Autónoma Metropolitana Iztapalapa, CDMX, México; 4Departamento de Física, Facultad de Ciencias, Universidad Nacional Autónoma de México, CDMX, México; 5Department of Psychology, University of Washington Guthrie Hall (GTH), Seattle, WA, USA; 6Departamento de Neuromorfología Funcional, Dirección de Investigaciones en Neurociencias, Instituto Nacional de Psiquiatría Ramón de la Fuente Muñiz, CDMX, México; 7Brain Health Imaging Centre, Centre for Addiction and Mental Health, Toronto, ON, Canada; 8Department of Psychiatry, University of Toronto, Toronto, ON, Canada; 9Laboratorio de Psiquiatría Experimental, Instituto Nacional de Neurología y Neurocirugía Manuel Velasco Suárez, CDMX, MéxicoCorrespondence: Francisco Pellicer, Dirección de Investigaciones en Neurociencias, Instituto Nacional de Psiquiatría Ramón de la Fuente Muñiz, Calzada México Xochimilco 101, San Lorenzo Huipulco, Alcaldía Tlalpan, CDMX, 14370, México, Tel +52 55 41605063, Email pellicer@imp.edu.mxObjective: Pain constitutes an essential alarm for preserving the organism’s integrity. Damage to the nervous system produces a pathological condition known as neuropathic pain.Purpose: Blood oxygenation level-dependent (BOLD) and functional magnetic resonance imaging (fMRI) have been widely used to map neuroanatomy and the active regions of interest (ROI) of nociceptive processing. Our study explored the brain’s BOLD response in rats after thermal noxious stimulation, immediately after sciatic nerve damage and during 75 minutes after surgical lesion of the sciatic nerve.Methods: Nine male Wistar rats were tested; the experiments were performed on a 7-Tesla /21-cm Varian Agilent system. This approach allowed, for the first time, to measure in vivo the BOLD changes in brain regions involved with the pain process: cingulated (ACC), somatosensory (S1), and insular cortices (IC), as well as thalamus (Th) and ventral tegmental area (VTA) related with acute thermal pain and during the early stages of sciatic denervation that produce neuropathic pain.Results: During thermonociception scan, all subjects showed BOLD activation in the ROIs determined as ACC, S1, Th, IC and VTA. After denervation, these regions continued to show activation with a slow decrement in intensity for the duration of the experiment. The results suggest that these brain structures are overactive during the genesis of neuropathic pain.Conclusion: The study shows for the first time continuous activation of the pain matrix following an acute thermal nociceptive stimulus followed by neuropathic damage. These results have given insight into the early stages of the development of neuropathic pain in vivo.Keywords: fMRI, resting state, neuropathic pain, pain matrix, chronic pain, acute pain

Ulises Coffeen, Francisco Pellicer Research in Neurosciences, Instituto Nacional de Psiquiatría Ramón de la Fuente Muñiz, Mexico City, México Abstract: Salvia divinorum is a herbal plant native to the southwest region of Mexico. Traditional preparations of this plant have been used in illness treatments that converge with inflammatory conditions and pain. Currently, S. divinorum extracts have become popular in several countries as a recreational drug due to its hallucinogenic effects. Its main active component is a diterpene named salvinorin A (SA), a potent naturally occurring hallucinogen with a great affinity to the κ opioid receptors and with allosteric modulation of cannabinoid type 1 receptors. Recent biochemical research has revealed the mechanism of action of the anti-inflammatory and analgesic effect of SA at the cellular and molecular level. Nevertheless, because of their short-lasting and hallucinogenic effect, the research has focused on discovering a new analogue of SA that is able to induce analgesia and reduce inflammation with a long-lasting effect but without the hallucinatory component. In this review, we explore the role of S. divinorum, SA and its analogues. We focus mainly on their analgesic and anti-inflammatory roles but also mention their psychoactive properties. Keywords: Salvia divinorum, salvinorin A, pain, inflammation, psychoactivity