introduction: deficiency in mu opioid receptor signaling pathway is partially responsible for morphine tolerance. this deficiency may be due to uncoupling of opioid receptors and related g proteins, which in turn, it may be caused by their structural changes such as phosphorylation or by decreasing their abundance. in this study, we tried to investigate the effect of chronic administration of m...

BACKGROUND The development of analgesic tolerance following chronic morphine administration can be a significant clinical problem. Preclinical studies demonstrate that chronic morphine administration induces spinal gliosis and that inhibition of gliosis prevents the development of analgesic tolerance to opioids. Many studies have also demonstrated that ultra-low doses of naltrexone inhibit the ...

Body temperature and pituitary-adrenal responses to restraint (15 min or 4 h) stress were evaluated in nondependent and morphine-dependent rats. Male Sprague-Dawley rats were treated twice daily with increasing doses of morphine (10-100 mg/kg, s.c.) for 16 days. Transmitters were implanted in the peritoneal cavity to monitor body temperature and blood was collected for hormone assays. Acute wit...

There is growing evidence indicating that neuronal calcium channels play an important role in the mechanism of morphine dependence. In this study, the effects of acute and chronic administration of nitrendipine on naloxone precipitated morphine withdrawal signs were investigated. Mice were rendered dependent to morphine by subcutaneous injection of morphine over a period of 5 days. In chronic s...

Tyrosine hydroxylase activity in slices of caudate nucleus was increased by morphine (100 mg/kg i.p.) administered to naive mice. During chronic treatment with morphine tolerance developed to this effect and 36 h after the final chronic morphine injection there was a decrease in enzyme activity in this area. There was no change in tyrosine hydroxylase activity in slices of diencephalon, brainst...

Ross GR, Gade AR, Dewey WL, Akbarali HI. Opioid-induced hypernociception is associated with hyperexcitability and altered tetrodotoxin-resistant Na channel function of dorsal root ganglia. Am J Physiol Cell Physiol 302: C1152–C1161, 2012. First published December 21, 2011; doi:10.1152/ajpcell.00171.2011.—Opiates are potent analgesics for moderate to severe pain. Paradoxically, patients under ch...

Neuroplasticity in the mesolimbic dopaminergic system is critical for behavioral adaptations associated with opioid reward and addiction. These processes may be influenced by cholinergic transmission arising from the laterodorsal tegmental nucleus (LDTg), a main source of acetylcholine to mesolimbic dopaminergic neurons. To examine this possibility we asked if chronic systemic morphine administ...

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...

Background: Empathy is the capability to represent the mental and emotional states of other subjects.Previous studies have demonstrated a possible correlation between morphine addiction and altered empathyresponse in morphine-addicted subjects. This study was performed to evaluate the effect of chronic morphineexposure as an animal model of morphine addiction on empathic changes in affective an...

The clinical use of morphine to reduce pain is limited because of its drug tolerance, dependence and addiction. In the present study, the tree shrews (Tupaia belangeri chinensis) developed morphine tolerance and chronic morphine dependence by morphine injections with increasing doses (5, 10, 15, 20 mg/kg body weight for 7 days). Meanwhile, the naloxone (1.25 mg/kg body weight)-induced condition...