Increased anxiety-like behaviors in rats experiencing chronic inflammatory pain.

TitleIncreased anxiety-like behaviors in rats experiencing chronic inflammatory pain.
Publication TypeJournal Article
Year of Publication2012
AuthorsParent, AJ, Beaudet, N, Beaudry, H, Bergeron, J, Bérubé, P, Drolet, G, Sarret, P, Gendron, L
JournalBehav Brain Res
Date Published2012 Apr 01
KeywordsAnalysis of Variance, Animals, Anti-Anxiety Agents, Anxiety, Chronic Disease, Dark Adaptation, Diazepam, Disease Models, Animal, Exploratory Behavior, Freund's Adjuvant, Functional Laterality, Hyperalgesia, Inflammation, Interpersonal Relations, Male, Morphine, Motor Activity, Mycobacterium, Narcotics, Pain, Pain Threshold, Rats, Rats, Sprague-Dawley, Time Factors

For many patients, chronic pain is often accompanied, and sometimes amplified, by co-morbidities such as anxiety and depression. Although it represents important challenges, the establishment of appropriate preclinical behavioral models contributes to drug development for treating chronic inflammatory pain and associated psychopathologies. In this study, we investigated whether rats experiencing persistent inflammatory pain induced by intraplantar injection of complete Freund's adjuvant (CFA) developed anxiety-like behaviors, and whether clinically used analgesic and anxiolytic drugs were able to reverse CFA-induced anxiety-related phenotypes. These behaviors were evaluated over 28 days in both CFA- and saline-treated groups with a variety of behavioral tests. CFA-induced mechanical allodynia resulted in increased anxiety-like behaviors as evidenced by: (1) a significant decrease in percentage of time spent and number of entries in open arms of the elevated-plus maze (EPM), (2) a decrease in number of central squares visited in the open field (OF), and (3) a reduction in active social interactions in the social interaction test (SI). The number of entries in closed arms in the EPM and the distance traveled in the OF used as indicators of locomotor performance did not differ between treatments. Our results also reveal that in CFA-treated rats, acute administration of morphine (3mg/kg, s.c.) abolished tactile allodynia and anxiety-like behaviors, whereas acute administration of diazepam (1mg/kg, s.c) solely reversed anxiety-like behaviors. Therefore, pharmacological treatment of anxiety-like behaviors induced by chronic inflammatory pain can be objectively evaluated using multiple behavioral tests. Such a model could help identify/validate alternative potential targets that influence pain and cognitive dimensions of anxiety.

Alternate JournalBehav. Brain Res.
PubMed ID22245257
PubMed Central IDPMC3848972
Grant List84538-1 / / Canadian Institutes of Health Research / Canada
/ / Canadian Institutes of Health Research / Canada