It has been shown that stress and chronic pain could prevent the development of tolerance to morphine analgesia, which appears to be related to the activation of hypothalamus–pitutitary–adrenal (HPA) axis, activation of neuroendocrine systems and changes in neurochemical levels. Moreover, the involvement of nitric oxide (NO) in the development of tolerance to morphine analgesia has been implica...

BACKGROUND In the present study, the effect of dextromethorphan on antinociception and tolerance induced by water swim-stress in the formalin test was investigated. METHODS Swim-stress at 8 masculineC induces antinociception in both phases of the formalin test. Intraperitoneal administration of dextromethorphan (60 mg/kg) also induces antinociception in the second phase of the formalin test. ...

BACKGROUND Lithium has been shown to relieve mania and induce antinociception. In the present study, swim stress at 8C induced antinociception in both phases of the formalin test. Intraperitoneal administration of lithium chloride (LiCl) (0.05, 0.25, and 0.5 mg/kg) also induced antinociception in both phases of the formalin test. METHODS Antinociception was assessed by the formalin test metho...

objective(s): there are many reports about the role of rostral ventromedial medulla (rvm) in modulating stress-induced analgesia (sia). in the previous study we demonstrated that temporal inactivation of rvm by lidocaine potentiated stress-induced analgesia. in this study, we investigated the effect of permanent lesion of the rvm on sia by using formalin test as a model of acute inflammatory pa...

in the present study, interactions of dopamine receptor agonists and antagonists with water swimming stress (wss) on naloxone-induced jumping in morphine-dependent mice were examined. mice were rendered dependent as described in the methods section. the opioid receptor antagonist, naloxone (1 mg/kg), was injected to elicit jumping (as a withdrawal sign). the first group exposed to wss in the pr...

Introduction: The formalin test is the most accepted chemical test for evaluation of nociception. It requires the injection of an adequate amount of formalin into the surface of the hindpaw. Formalin test consists of phase 1 (0-7 min) and phase 2 (15-60) in which the animal shows painful behaviors. These phases are separated with a quiet phase named interphase, in which the nociceptive respon...

We studied the influence of imipramine on the duration of immobility in chronic forced-swim-stressed rats. Both single and chronic administration of imipramine potently shortened immobility in naive rats during forced-swim testing. However, chronic, 14-day forced-swim stress testing blocked the immobility-decreasing effect induced by a single administration of imipramine. When imipramine was ad...

The dorsal raphe nucleus (DR)-serotonin (5-HT) system has been implicated in depression and is dramatically affected by swim stress, an animal model with predictive value for antidepressants. Accumulating evidence implicates the stress-related neuropeptide corticotropin-releasing factor (CRF) in the effect of swim stress on this system. This study investigated neural circuits within the DR that...

Alterations in brain activity patterns were assessed in response to swim stress by immunocytochemical detection of Fos-like immunoreactivity (Fos-LI) and high-resolution autoradiographic imaging of 14C-2-deoxyglucose (2-DG) uptake. The stress paradigm investigated was a classic behavioral screen for antidepressant drug activity, the forced swim test. One of the most pronounced effects produced ...

Stress is known to elicit pain relief, a phenomenon referred to as stress-induced analgesia. Based on stress parameters, opioid and non-opioid intrinsic pain inhibitory systems can be activated. In the present study, we assessed whether changing the duration of stress would affect the involvement of endogenous opioids in antinociception elicited by swim in warm water (32 °C), known to be opioid...