Nandrolone decreases mu opioid receptor expression in SH-SY5Y human neuroblastoma cells

Sex differences in opioid receptor mediated effects: Role of androgens

An abundance of data indicates there are sex differences in endogenous opioid peptides and opioid receptors, leading to functional differences in sensitivity to opioid receptor mediated behaviors between males and females. Many of these sex differences are mediated by the effects of gonadal hormones on the endogenous opioid system. Whereas much research has examined the role of ovarian hormones on opioid receptor mediated endpoints, comparatively less research has examined the role of androgens. This review describes what is currently known regarding the influence of androgens on opioid receptor mediated endpoints and how androgens may contribute to sex differences in these effects. The review also addresses the clinical implications of androgenic modulation of opioid receptor mediated behaviors and suggests future lines of research for preclinical and clinical investigators. We conclude that further investigation into androgenic modulation of opioid receptor mediated effects may lead to new options for addressing conditions such as chronic pain and substance use disorders.

Chronic administration of nandrolone increases susceptibility to morphine dependence without correlation with LVV-hemorphin 7 in rats

LVV-hemorphin 7 (LVVYPWTQRF; LVV-H7), an N-terminal fragment of the β-chain of hemoglobin cleaved by cathepsin D/pepsin, is an atypical endogenous opioid peptide that is found in high concentration in blood. LVV-H7 acts as a μ-opioid agonist and an inhibitor of insulin-regulated aminopeptidase. Subchronic administration of anabolic androgenic steroids (AAS) has been clinically proven to induce the synthesis of erythrocytes and increase hemoglobin concentrations. Patients with a history of AAS abuse are more susceptible to opioid abuse. We hypothesized that this association could be at least partially attributed to the sensitization of the mesocorticolimbic dopaminergic pathway by LVV-H7. Using the conditioned place preference test and neurochemical analysis, we investigated the possible mechanism underlying the effect of chronic nandrolone administration on morphine-induced reward and its correlation with LVV-H7 in rats. Either LVV-H7 may not sensitize the rewarding neural circuits or its inhibition on locomotor activity could mask reward-related behaviors. Chronic nandrolone pretreatment indeed caused a significant reward by low dose morphine, which did not cause any reward in control rats. However, coadministration of anti-LVV-H7 antiserum with nandrolone did not block this effect. This may rule out the possibility of the involvement of LVV-H7 in the action of nandrolone to intensify morphine-induced reward. Moreover, the serum level of LVV-H7 was mildly increased in response to chronic nandrolone administration in our animal model. According to the current clinical observations, we may conclude that the chronic administration of nandrolone can increase susceptibility to morphine dependence, but that this effect is not related to elevated LVV-H7.

Androgens and opiates: testosterone interaction with morphine self-administration in male rats

Abuse of anabolic androgenic steroids (AAS) and opioids intersects in athletics. Evidence from humans and animals suggests that AAS may act in the brain through opioidergic mechanisms, and may potentiate effects of opioids. To determine whether AAS enhance motivation for opioid intake, in this study, male rats were treated chronically for 6 weeks with high levels of testosterone (7.5 mg/kg) or vehicle subcutaneously, and they were tested for morphine self-administration under fixed-ratio (FR) and progressive-ratio (PR) schedules. Initially, rats received chronic morphine infusion (16.8-50 mg/kg/day) over 7 days. Subsequently, rats were tested for morphine self-administration (3.2 mg/kg) 6 h/day for 3 days under an FR1 schedule, and for 7 days under a PR 9-4 schedule. Under the FR1 schedule, controls self-administered more morphine (95.9±8.5 mg/kg) than testosterone-treated rats (63.2±7.2 mg/kg; P<0.05). Under the PR schedule, there was no effect of testosterone on morphine intake or operant responding (26.7±5.7 responses vs. 30.9±5.9 responses for vehicle; NS). To determine whether testosterone enhances morphine sedation, additional rats were treated with testosterone or vehicle and evaluated for locomotor behavior and rearing activity over 30 min in response to saline or 10 mg/kg morphine. Morphine inhibited locomotor activity and rearing; testosterone selectively reduced rearing behavior, but did not alter locomotor behavior. These results suggest that testosterone does not increase motivation for morphine.

Sex differences in opioid analgesia and addiction: interactions among opioid receptors and estrogen receptors

Opioids are widely used as the pain reliever and also notorious for being addictive drugs. Sex differences in the opioid analgesia and addiction have been reported and investigated in human subjects and animal models. Yet, the molecular mechanism underlying the differences between males and females is still unclear. Here, we reviewed the literature describing the sex differences in analgesic responses and addiction liabilities to clinically relevant opioids. The reported interactions among opioids, estrogens, opioid receptors, and estrogen receptors are also evaluated. We postulate that the sex differences partly originated from the crosstalk among the estrogen and opioid receptors when stimulated by the exogenous opioids, possibly through common secondary messengers and the downstream gene transcriptional regulators.

Interactions between opioids and anabolic androgenic steroids: implications for the development of addictive behavior

Over the past decades, research on doping agents, such as anabolic androgenic steroids (AAS), has revealed that these compounds are often used in combination with other drugs of abuse. It seems that misuse of AAS probably involves more than a desire to enhance appearance or sports performance and studies have revealed that steroids are commonly connected with alcohol, opioids, tobacco, and psychotropic drugs. We have observed that AAS may interact with the endogenous opioids, excitatory amino acids, and dopaminergic pathways involved in the brain reward system. Furthermore, our studies provide evidence that AAS may induce an imbalance in these signal systems leading to an increased sensitivity toward opioid narcotics and central stimulants. In fact, studies performed in various clinics have shown that individuals taking AAS are likely to get addicted to opioids like heroin. This chapter reviews current knowledge on interactions between AAS and endogenous as well as exogenous opioids based not only on research in our laboratory but also on research carried out by several other clinical and preclinical investigators.

Propofol increases µ-opioid receptor expression in SH-SY5Y human neuroblastoma cells

The aim of the present study was to explore the effect of propofol, a intravenous sedative-hypnotic agent used widely in inducing and maintaining anesthesia, on µ-opioid receptor (MOR) expression in a human neuronal cell line. SH-SY5Y human neuroblastoma cells were treated with various concentrations of propofol (1, 5, 10 or 20 µM) for different lengths of time (6, 12 or 24 h). Real-time quantitative RT-PCR showed that at a concentration range of 1-10 µM, propofol increased MOR mRNA levels in a statistically significant dose- and time-dependent manner within 12 h of treatment. Western blot analyses demonstrated that propofol treatment for 12 h dose-dependently increased the MOR protein levels. In the 12-h SH-SY5Y-treated cells, propofol dose-dependently increased MOR density (Bmax) in the cell membranes. In addition, in the presence of the transcription inhibitor actinomycin D (1 mg/ml), propofol (10 µM) had no significant effect on the MOR mRNA levels over time. The results suggested that propofol dose- and time-dependently enhances MOR expression in SH-SY5Y human neuroblastoma cells at the transcriptional level, leading to an increased density of ligand-binding MORs in the cell membranes. This study demonstrated for the first time a link between propofol and the opioid system, thereby providing new insights into propofol mechanism of action and potential for abuse.

Endogenous opiates and behavior: 2008

This paper is the 31st consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2008 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).

Differential effects of steroids on the synthesis of polyunsaturated fatty acids by human neuroblastoma cells

Polyunsaturated fatty acids (PUFA) are crucial for proper functioning of cell membranes, particularly in brain. Biologically important PUFA include docosahexaenoic acid (n-3 series) and arachidonic acid (n-6 series) which can be formed from their respective dietary essential precursors, alpha-linolenic acid (ALA) and linoleic acid (LA). Steroid hormones are thought to modulate PUFA synthesis in humans but whether they regulate PUFA status in brain and/or in neural membranes is unknown. In human neuroblastoma SH-SY5Y cells, we compared the effect of estradiol, testosterone, and progesterone on PUFA synthesis. Cells were incubated with ALA and/or LA 7 microM in combination with estradiol, testosterone, or progesterone at 10 nM without serum. The fatty acid composition was determined by gas chromatography and the mRNA expression of genes involved in PUFA metabolism by real-time RT-PCR. Estradiol affected both the n-3 and the n-6 PUFA conversion, the n-3 PUFA pathway being more sensitive to the estradiol treatment. In ALA-supplemented cells, estradiol increased while testosterone decreased the long-chain n-3 PUFA content (+17% and -15%, respectively) and the mRNA expression of the Delta5-desaturase (+11% and -9%), these two events being strongly correlated. Progesterone did not affect the PUFA composition. The positive effect of estradiol was blocked by the estrogen receptor antagonist ICI-182,780. We conclude that steroids have differential effects on PUFA synthesis and that their mode of action could involve the modulation of the Delta5-desaturase mRNA expression in neuroblastoma cells. These results help our understanding of the regulation of brain PUFA metabolism by steroid hormones.