Mice were rendered tolerant and dependent to morphine by subcutaneous injection of morphine over a period of 5 days. The effects of acute and chronic administration of dihydropyridine calcium channel antagonist nifedipine on the development of tolerance and naloxone-precipitated morphine withdrawal signs were investigated. A single injection of nifedipine proved to be effective in inhibiti...

We investigated the effects of morphine and other agonists on the human mu opioid receptor (MOP) expressed in M2 melanoma cells, lacking the actin cytoskeleton protein filamin A and in A7, a subclone of the M2 melanoma cells, stably transfected with filamin A cDNA. The results of binding experiments showed that after chronic morphine treatment (24 h) of A7 cells, MOP-binding sites were down-reg...

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...

Lithocholic acid (LCA) deposited in human livers always induces drastic pains which need analgesic drug, like morphine to release. Our research showed that LCA can effectively inhibit uridine 5'-diphospho-glucuronosyltransferase 2B7 (UGT2B7) in morphine tolerance-like human normal liver cells, HL-7702, then increase μ-opioid receptor (MOR) and calcium-calmodulin dependent protein kinase IIα (Ca...

Chronic morphine administration decreases the size of dopamine (DA) neurons in the ventral tegmental area (VTA). These transient morphological changes are accompanied by a reduced sensitivity of morphine-induced conditioned place preference (CPP) after chronic exposure to the drug. In this study we examined alterations in the firing rate of DAergic neurons by means of extracellular recording fo...

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: Stress inhibits the development of tolerance to morphine analgesia via activating Hypothalamic- Pituitary-Adrenal (HPA) axis. Modified catecholamine systems have been reported following morphine tolerance development. In the current study we tried to evaluate changes in the gene expression levels for MAO-A, MAO-B, COMT and thyrosine hydroxylase (TyH) enzymes following chronic p...

Various physiological parameters including level of sex steroids undergo alterations following chronic administration of morphine. In this study, the effect of chronic administration of morphine on phasic and tonic pain was studied in morphine-dependent male and female rats in the presence and absence of gonads using formalin test. In addition, for evaluation of differences in dependency, withd...

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...

Chronic pain, including cancer-related pain, is a pain condition often caused by inflammation or dysfunctional nerves. Chronic pain treatment poses a significant health care challenge, where opioids especially morphine are widely used and patients often develop tolerance over time with aggravated pain. microRNA (miRNA) is known to play important roles in regulating gene expressions in the nervo...