BACKGROUND Although alterations in not only the pain sensitivity but also the analgesic effects of opioids have been reported under conditions of stress, the influence of unpredictable chronic mild stress (UCMS) on the antinociceptive effects of opioid analgesics remains to be fully investigated. The present study examined the influence of UCMS on the thermal pain sensitivity and antinociceptiv...

Opiates, one of the oldest known drugs, are the benchmark for treating pain. Regular opioid exposure also induces euphoria making these compounds addictive and often misused, as shown by the current epidemic of opioid abuse and overdose mortalities. In addition to the effect of opioids on their cognate receptors and signaling cascades, these compounds also induce multiple adaptations at cellula...

Morphine and delta9-tetrahydrocannabinol (THC) produce antinociception via mu opioid and cannabinoid CB1 receptors, respectively, located in central nervous system (CNS) regions including periaqueductal gray and spinal cord. Chronic treatment with morphine or THC produces antinociceptive tolerance and cellular adaptations that include receptor desensitization. Previous studies have shown that a...

We investigated the in vivo dynamics and analgesic effect of morphine using an adjuvant-induced arthritis (AA) rat as a model of chronic inflammation. Morphine generally binds to μ-opioid receptors in the brain to exert its effects. After several minutes, it is metabolized by glucuronidation via a UDP-glucuronosyltransferase (UGT). Here, we showed that in AA rats, UGT activity in liver microsom...

Chronic morphine exposure results in degradation of the functional properties of cortical cells. However, little evidence has been reported about the effect of morphine on the temporal properties of the visual system. We compared the visual response latency of different cells of the lateral geniculate nucleus (LGN) in morphine (10 mg/mL)- and saline-treated cats. Morphine-treated cats were give...

background and objective: today, opioids are used to control and relieve acute and chronic pain. however, the incidence of both tolerance and dependence phenomena for these drugs is a major problem. so, in this study, the combination effect of haloperidol and methadone on the acquisition and expression of morphine dependence and tolerance was examined.    materials and methods: ninety-eight mic...

Diabetes is one of the most common diseases in all societies including Iran. One of its important complications is the neuropathic pain, which can be relieved by opioid drugs such as morphine. Opioid therapy is restricted due to development of tolerance and physical or mental dependence. In this study, the effect of diabetes on morphine analgesia and development of morphine tolerance and depend...

Background: There is growing evidence indicating that neuronal calcium channels play an important role in the mechanism of Morphine dependence. Objective: To investigate the acute and long-term effects of Verapamil in Morphine dependent mice. Methods: Mice were rendered dependent on Morphine by subcutaneous injection of Morphine over a period of 5 days. The effects of acute and chronic administ...

Opioid agonists such as morphine have been found to exert excitatory and inhibitory receptor-mediated effects at low and high doses, respectively. Ultra-low doses of opioid antagonists (naloxone and naltrexone), which selectively inhibit the excitatory effects, have been reported to augment systemic morphine analgesia and inhibit the development of tolerance/physical dependence. This study inve...

BACKGROUND Nonsteroidal antiinflammatory drugs are commonly used to treat postoperative and chronic pain. Animal studies suggest that these drugs act, in part, by blocking prostaglandin production in the spinal cord. The authors tested intrathecal ketorolac in patients with chronic or postoperative pain. METHODS After approval of the institutional review board and the Food and Drug Administra...