title: Monoarthritis-induced emotional and cognitive impairments in rats are sensitive to low systemic doses or intra-amygdala injections of morphine.
abstract: Chronic pain is a multidimensional experience that not only includes changes in nociception but also impairments in emotional and cognitive functions, not often taken into account in preclinical research. The present study investigated emotional and cognitive impairments in an animal model of persistent inflammatory pain as well as the involvement of the basolateral complex (BLC) of the amygdala in these components. Monoarthritis was induced by intra-articular injection of complete Freund׳s adjuvant. Mechanical hypersensitivity, anxiety and depressive-like behaviours as well as cognitive capacities were assessed using several tests, such as von Frey, social interaction, open field, saccharin preference, spatial and social recognition memory tests. The effects of morphine administered systemically or into the BLC of the amygdala were also studied. Monoarthritic rats exhibited mechanical hypersensitivity, anxiety and depressive-like behaviours as well as cognitive impairments. Whereas low systemic doses and intra-BLC infusion of morphine failed to reduce mechanical hypersensitivity, they reversed monoarthritis-induced anxiety-like behaviours and cognitive impairments. Our findings further support a crucial role of amygdala in the effect of morphine on emotional/cognitive components of pain and not on mechanical hypersensitivity. Finally, our study highlights the interest of a multi-behavioural approach in the assessment of pain and the analgesic effect of drugs.
authors.affiliation: Clermont Université, Université d׳Auvergne, NEURO-DOL, BP 10448, F-63000 Clermont-Ferrand, France; Clermont-Ferrand Inserm, U1107, F-63001 Clermont-Ferrand BP 10448, F-63000 Clermont-Ferrand, France. Electronic address: stephanie.gregoire.sg@gmail.com.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Grégoire
authors.affiliation: Clermont Université, Université d׳Auvergne, NEURO-DOL, BP 10448, F-63000 Clermont-Ferrand, France; Clermont-Ferrand Inserm, U1107, F-63001 Clermont-Ferrand BP 10448, F-63000 Clermont-Ferrand, France. Electronic address: as.wattiez@gmail.com.
authors.forename: Anne-Sophie
authors.initials: AS
authors.lastname: Wattiez
authors.affiliation: Clermont Université, Université d׳Auvergne, NEURO-DOL, BP 10448, F-63000 Clermont-Ferrand, France; Clermont-Ferrand Inserm, U1107, F-63001 Clermont-Ferrand BP 10448, F-63000 Clermont-Ferrand, France. Electronic address: monique.etienne@udamail.fr.
authors.forename: Monique
authors.initials: M
authors.lastname: Etienne
authors.affiliation: Clermont Université, Université d׳Auvergne, NEURO-DOL, BP 10448, F-63000 Clermont-Ferrand, France; Clermont-Ferrand Inserm, U1107, F-63001 Clermont-Ferrand BP 10448, F-63000 Clermont-Ferrand, France. Electronic address: fabien.marchand@udamail.fr.
authors.forename: Fabien
authors.initials: F
authors.lastname: Marchand
authors.affiliation: Clermont Université, Université d׳Auvergne, NEURO-DOL, BP 10448, F-63000 Clermont-Ferrand, France; Clermont-Ferrand Inserm, U1107, F-63001 Clermont-Ferrand BP 10448, F-63000 Clermont-Ferrand, France. Electronic address: denis.ardid@udamail.fr.
authors.forename: Denis
authors.initials: D
authors.lastname: Ardid
mesh_terms: D000701:Analgesics, Opioid / Q000008:administration & dosage*; D000818:Animals; D001169:Arthritis, Experimental / Q000139:chemically induced / Q000523:psychology*; D066272:Basolateral Nuclear Complex / Q000503:physiopathology*; D003071:Cognition; D003072:Cognition Disorders / Q000523:psychology*; D004195:Disease Models, Animal; D004644:Emotions; D005518:Food Preferences; D005620:Freund's Adjuvant; D006930:Hyperalgesia / Q000523:psychology*; D007267:Injections; D007398:Interpersonal Relations; D008297:Male; D018782:Maze Learning; D009020:Morphine / Q000008:administration & dosage*; D010146:Pain / Q000523:psychology; D017207:Rats, Sprague-Dawley; D012439:Saccharin
chemical_list: D000701:Analgesics, Opioid; D009020:Morphine; D005620:Freund's Adjuvant; D012439:Saccharin
keywords: Amygdala; Chronic inflammatory pain; Cognition; Emotion; Morphine; Rats