Premium
Effects of intra‐basolateral amygdala administration of rimonabant on nociceptive behaviour and neuronal activity in the presence or absence of contextual fear
Author(s) -
Roche Michelle,
Johnston Patrick,
Mhuircheartaigh Orla Ní,
Olango Weredeselam M.,
Mackie Kenneth,
Finn David P.
Publication year - 2010
Publication title -
european journal of pain
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.305
H-Index - 109
eISSN - 1532-2149
pISSN - 1090-3801
DOI - 10.1016/j.ejpain.2009.08.009
Subject(s) - basolateral amygdala , nociception , cannabinoid receptor , rimonabant , rostral ventromedial medulla , periaqueductal gray , hyperalgesia , cannabinoid , amygdala , psychology , neuroscience , allodynia , agonist , medicine , receptor , central nervous system , midbrain
The basolateral amygdala (BLA) contains a high density of cannabinoid CB 1 receptors and is critically involved in pain and fear‐related behaviour. We investigated the effects of bilateral intra‐BLA administration of the CB 1 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.