Nociception- and anxiety-like behavior in rats submitted to different periods of restraint stress

• Published in: Physiology & behavior 2006-04, Vol.87 (4), p.643-649
• Main Authors: Gameiro, Gustavo Hauber, Gameiro, Paula Hauber, da Silva Andrade, Annicele, Pereira, Lígia Ferrinho, Arthuri, Mariana Trevisani, Marcondes, Fernanda Klein, de Arruda Veiga, Maria Cecília Ferraz
• Format: Article
• Language: English
• Subjects: Acute Disease; Adrenocorticotropic Hormone - blood; Analgesics, Opioid - pharmacology; Animals; Anxiety; Anxiety - blood; Anxiety - etiology; Biological and medical sciences; Chronic Disease; Cortisone - blood; Disease Models, Animal; Emotions; Exploratory Behavior; Facial pain; Fluoxetine - pharmacology; Fundamental and applied biological sciences. Psychology; Male; Morphine - pharmacology; Pain - blood; Pain Threshold - drug effects; Perception; Proprioception. Interoception. Pain perception; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Rats; Rats, Wistar; Receptors, Opioid - agonists; Restraint, Physical; Serotonin Uptake Inhibitors - pharmacology; Stress; Stress, Psychological - blood; Stress, Psychological - complications; Stress, Psychological - psychology; Temporomandibular disorders; Time Factors
• ISSN: 0031-9384; 1873-507X
• DOI: 10.1016/j.physbeh.2005.12.007

The aim of this study was to evaluate the effect of acute, sub-chronic and chronic stress on nociception induced by formalin injection in rats' temporomandibular joint (TMJ). It was evaluated the relation between blood levels of adrenocorticotropin, corticosterone, the levels of anxiety and nociceptive responses recorded after different stress protocols. Animals were initially submitted to acute restraint stress (15; 30 min and 1 h), or exposed to sub-chronic (3 days—1 h/day) or chronic stress (40 days—1 h/day). Then, animals were (1) killed immediately to collect blood for hormonal determinations; or (2) submitted to the elevated plus-maze to evaluate anxiety; or (3) submitted to the TMJ formalin test to evaluate nociception. It was also evaluated the role of serotoninergic and opioid systems in nociceptive changes induced by stress. For this, the serotonin-selective reuptake inhibitor (fluoxetine 10 mg/kg) and the opioid agonist (morphine 1–5 mg/kg) were administered before the nociception test. All stress protocols significantly raised the levels of ACTH or corticosterone, as well as the anxiety behavior. In relation to nociception, the chronic stressed animals showed an increase in nociceptive responses (hyperalgesia). In this group, there was a reduction in the morphine analgesic effects, suggesting dysfunction in the endogenous opioid system. Fluoxetine had an analgesic effect in both stressed and control groups, although this effect was more evident in the stressed group. It was concluded that stress-induced hyperalgesia may result from changes in the serotoninergic and opioid systems, which can explain, at least in part, the important link between stress and orofacial pain.