Increasing Pain Sensation Eliminates the Inhibitory Effect of Depression on Evoked Pain in Rats.

Although previous studies have suggested that depression may be associated with inhibition of evoked pain but facilitation of spontaneous pain, the mechanisms underlying these relationships are unclear. The present study investigated whether the difference between evoked and spontaneous pain on sensory (descending inhibition) and affective (avoidance motivation) components contributes to the divergent effects of depression on them. Depressive-like behavior was produced in male Wistar rats by unpredictable chronic mild stress (UCMS).

Chronic administration of 5-HT1A receptor agonist relieves depression and depression-induced hypoalgesia.

Previous studies have shown that depressed patients as well as animal models of depression exhibit decreased sensitivity to evoked pain stimuli, and serotonin is indicated to be involved in depression-induced hypoalgesia. The purpose of this study was to investigate the potential role of 5-HT1A receptor in the depression-induced hypoalgesia. Acute or chronic administration of 5-HT1A receptor agonist, 8-OH-DPAT, was performed in olfactory bulbectomy (OB) and sham-operated rats.

Depressive-like history alters persistent pain behavior in rats: Opposite contribution of frontal cortex and amygdala implied.

Numerous studies have shown that pain perception is strongly influenced by depression. However, very few studies have examined whether pain perception is altered in the remission period of depression, and what role the fronto-limbic circuits may play in the behavioral changes associated with remission. Using an unpredictable chronic mild stress (UCMS) animal model of depression, the present study investigated pain-related behaviors in rats with prior exposure to a UCMS stimulus.

Increased thermal and mechanical nociceptive thresholds in rats with depressive-like behaviors.

Clinical observations suggest that depressed patients were less sensitive to experimental pain than healthy subjects. However, few animal studies are reported concerning the association of depression and pain. The purpose of this study was to investigate the effects of unpredictable chronic mild stress (UCMS) induced depression on the perceived intensity of painful stimulation in rats.

The differential effects of depression on evoked and spontaneous pain behaviors in olfactory bulbectomized rats.

Although it has been accepted that depression and pain are common comorbidities, their interaction is not fully understood. The current study was aimed to investigate the effects of depression on both evoked pain behavior (thermal-induced nociception) and spontaneous pain behavior (formalin pain) using an olfactory bulbectomy (OB) rat model of depression. Emotional behaviors were assessed by open field and Morris water maze tests.