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Roche, M,Johnston, P,Mhuircheartaigh, ON,Olango, WM,Mackie, K,Finn, DP
2010
May
European Journal Of Pain
Effects of intra-basolateral amygdala administration of rimonabant on nociceptive behaviour and neuronal activity in the presence or absence of contextual fear
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Pain Cannabinoid Conditioned fear cFos Rimonabant (SR141716A) ANTERIOR CINGULATE CORTEX STRESS-INDUCED ANALGESIA CANNABINOID-INDUCED ANTINOCICEPTION ROSTRAL VENTROMEDIAL MEDULLA CONDITIONED PLACE AVOIDANCE C-FOS EXPRESSION PERIAQUEDUCTAL GRAY RECEPTOR ANTAGONIST NMDA RECEPTORS DENTATE GYRUS
14
487
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The basolateral amygdala (BLA) contains a high density of cannabinoid CB1 receptors and is critically involved in pain and fear-related behaviour. We investigated the effects of bilateral intra-BLA administration of the CB1 receptor antagonist/inverse agonist, rimonabant, on formalin-evoked nociceptive behaviour, fear-conditioned behaviour including analgesia, and associated brain regional alterations in Fos expression in rats. Intra-BLA administration of rimonabant significantly reduced formalin-evoked nociceptive behaviour in the absence, but not presence, of conditioned fear. Rimonabant attenuated a formalin-evoked reduction in freezing while emitting 22 kHz ultrasonic vocalisation in the early part of the fear expression trial. Formalin-evoked nociceptive behaviour was associated with increased Fos immunoreactivity (FI) in the CA2/3 region of the hippocampus and rostral ventromedial medulla, effects attenuated by intra-BLA rimonabant. Formalin also decreased FI in the cingulate cortex, an effect which was not observed in fear-conditioned rats. Contextually-induced fear was associated with increased FI in the dorsal caudal periaqueductal grey in the absence, but not presence, of formalin-evoked nociceptive tone. In conclusion, bilateral intra-BLA administration of rimonabant reduces nociceptive behaviour in a model of tonic, persistent inflammatory pain, an effect associated with reduced activation of neurons in the CA2/3 hippocampus and rostral ventromedial medulla. The data also provide evidence for differential pain-and fear-related brain regional activity in the presence or absence of contextually-induced aversion and nociceptive tone. (C) 2009 European Federation of International Association for the Study of Pain Chapters. Published by Elsevier Ltd. All rights reserved.
DOI 10.1016/j.ejpain.2009.08.009
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