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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• 作者：Michelle Roche ; Patrick Johnston ; Orla Ní ; Mhuircheartaigh ; Weredeselam M. Olango ; Kenneth Mackie ; David P. Finn
• 关键词：Pain ; Cannabinoid ; Conditioned fear ; cFos ; Rimonabant (SR141716A)
• 刊名：European Journal of Pain
• 出版年：2010
• 出版时间：May 2010
• 年：2010
• 卷：14
• 期：5
• 页码：487-495
• 全文大小：541 K

文摘

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.