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...

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 response...

Stress and chronic pain have been shown to prevent the development of tolerance to morphine analgesia, which appears to be related to neuroendocrine activity and alternation in neurochemicals. Also the involvement of nitric oxide (NO) has been implicated in tolerance to morphine analgesia. In our pervious study, we showed that co-administration of swim stress (ss) with chronic morphine, prevent...

Introduction: Sub-chronic swim stress is known to induce a prolonged hyperalgesia, which is mediated through NMDA and opioid systems. Nitric oxide is a soluble gas, which acts as a retrograde messenger that modulates the release of mentioned neurotransmitters. It is also involved in nociception and memory. The aim of this study was to evaluate the role of NO pathway in nociception and memory...

Stress and chronic pain have been shown to prevent the development of tolerance to morphine analgesia, which appears to be related to neuroendocrine activity and alternation in neurochemicals. Also the involvement of nitric oxide (NO) has been implicated in tolerance to morphine analgesia. In our pervious study, we showed that co-administration of swim stress (ss) with chronic morphine, prevent...

Objective(s): Stress alters sensory and cognitive function in humans and animals. Angiotensin (AT) receptors have demonstrated well-established interactions in sets of physiological phenomena. AT1 receptors can play a part in stress-induced activation of hypothalamic-pituitary-adrenal (HPA) axis; besides angiotensinergic neurotransmission plays a pivotal role in stress-evoked physiological resp...

introduction: different mechanisms are involved in stress induced analgesia (sia) and hyperalgesia (sih). repeated stress induces development of tolerance to sia. the role of hpa axis and gs signaling pathway in these effects are investigated in the current study. methods: forced swim stress (5 min/day) in water (20±1 ºc) was employed to adult male wistar rats (200-250 g). the nociceptive thres...

Introduction: Despite significant progress in understanding pain control mechanism, there are numerous questions about central nervous mechanisms underlying stress-induced analgesia. The rostral ventromedial medulla (RVM) in the brainstem integrates a variety of functions, including pain modulation and pain perception. In the present study, we investigated the effect of temporary inactivatio...

Introduction: Some evidence demonstrates endogenous inhibitory pathways of pain involved in the interphase (phase between early and later phase) of the formalin test. We previously showed that swimming stress modulates the pain-related behaviors during the interphase of the formalin test. In this study, we evaluated the role of the endogenous opioid system in modulating nociceptive responses of...

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...