Introduction: Chronic morphine exposure can cause addiction and affect synaptic plasticity, but the underlying neural mechanisms of this phenomenon remain unknown. Herein we used electrophysiologic approaches in hippocampal CA1 area to examine the effect of chronic morphine administration on short-term plasticity. Methods: Experiments were carried out on hippocampal slices taken from either con...

introduction: methadone has been used as a drug to detoxify opioid tolerance. naloxane precipitated morphine withdrawal behaviours were attenuated by venlafaxine as an antidepressant. on the contrary, after detoxifying the opioids, spontaneous withdrawal syndrome may occur with pain sensitivity. therefore the present study aimed to examine the effects of chronic methadone (70 mg/kg, in drinking...

in this study, the effects of acute and chronic lithium on nociception induced by formalin and its interactions with morphine-induced analgesia were studied in mice. formalin test was selected to study nociception. subcutaneous injection of different doses of morphine (1.5, 3 and 6 mg/kg) induced analgesia in a dose dependent manner in both phases of the formalin test. intraperitoneal administr...

Opioid and non-opioid effects of acute and chronic morphine administration on behaviour, cardiovascular responses, cell proliferation and apoptosis and nitric-oxide synthase (NOS) activity were studied in rats. A novel score-point scale was introduced to quantify the signs of opioid withdrawal syndrome. NOS inhibitor L-NAME (NG-nitro-L-arginine methyl ester) was applied to reveal the role of NO...

Chronic opioid receptor (OR) activation by morphine causes distinct cellular adaptations responsible for the development of tolerance. The present study examines the effect of chronic morphine exposure on the ability of high-efficacy agonists to mediate delta-OR (DOR) and mu-OR (MOR) uncoupling and internalization, two regulatory mechanisms contributing to rapid desensitization of OR function. ...

Levels of tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine biosynthesis, are known to be upregulated in specific brain regions by chronic administration of drugs of abuse. Chronic morphine administration increases TH levels in the locus coeruleus and ventral tegmental area, whereas chronic cocaine administration increases TH levels in the ventral tegmental area only. While s...

morphine and tramadol which have analgesic effects can be administered acutely or chronically. this study tried to investigate the effect of these drugs at various times by using different methods of administration (intraperitoneal, oral, acute and chronic). sixty adult female rats were divided into six groups. they received saline, morphine or tramadol (20 to 125 mg/kg) daily for 15 days. a ho...

introduction: the aim of this study was to assess the effect of ca2+/calmodulin-dependent kinase iiα (camkiiα) inhibitor (kn-93) injection into the locus coeruleus (lc) on the modulation of withdrawal signs. we also sought to study the effect of chronic morphine administration on camkiiα activity in the rat lc. methods: the research was based on behavioral and molecular studies. in the behavior...

Previously, we have identified a number of morphine- and cyclic AMP-regulated phosphoproteins (MARPPs) in the rat locus coeruleus (LC) and other brain regions. We now show that one of these phosphoproteins, a 58 kDa protein designated MARPP-58, is tyrosine hydroxylase. First, MARPP-58 comigrates with immunolabeled, immunoprecipitated, and purified tyrosine hydroxylase on 1- and 2-dimensional el...