Stress- and morphine-induced elevations of plasma and tissue cholesterol in mice: reversal by naltrexone

Nalmefene, an opioid receptor modulator, aggravates atherosclerotic plaque formation in apolipoprotein E knockout mice by enhancing oxidized low-density lipoprotein uptake in macrophages

Nalmefene, an antagonist of mu- and delta-opioid receptors and a partial agonist of kappa-opioid receptors, has shown promise in reducing alcohol consumption among patients with alcohol dependence. Opioid receptors play pivotal roles in various physiological processes, including those related to peripheral inflammatory diseases such as colitis and arthritis, as well as functions in the immune system and phagocytosis. Atherosclerosis, a chronic inflammatory disease, progresses through the phagocytosis and uptake of oxidized low-density lipoprotein (oxLDL) by macrophages in atherosclerotic plaques. Despite this knowledge, it remains unclear whether nalmefene influences the formation of atherosclerotic plaques and increases the risk of serious cardiovascular events. This study aims to elucidate the impact of nalmefene on atherosclerosis in apolipoprotein E knockout (ApoE KO) mice and peritoneal macrophages in vitro. In this experiment, 8-week-old male ApoE KO mice were fed a high-fat diet intraperitoneally administered either vehicle (saline) or nalmefene (1 mg and 3 mg kg-1 day-1) for 21 days. Oil red O-staining and immunohistochemistry with an anti-MOMA2 (monocyte/macrophage) antibody showed that a dose-dependent increase in atherosclerotic plaque formation and augmentation of macrophage-rich plaque formation in ApoE-KO mice. Further investigations focused on the effects of nalmefene on the expression of scavenger receptor CD36 in RAW264.7 cells, conducted through western blotting analysis. Nalmefene demonstrated a significant increase in CD36 protein expression in RAW264.7 cells. To explore the impact on oxidized LDL uptake in peritoneal macrophages, cells were treated with nalmefene (300 μg/mL) for 24 h, followed by the addition of DiI-labeled oxLDL (DiI-oxLDL) for 4 h. Nalmefene significantly enhanced DiI-oxLDL uptake in macrophages. Additionally, treatment with nalmefene (300 μg/mL) for 24 h decreased the mRNA expression of mu-, delta-, and kappa-opioid receptors in RAW264.7 cells. In conclusion, nalmefene may augment oxLDL uptake by macrophages through increased CD36 expression and decreased opioid receptor, thereby contributing to atherosclerotic plaque formation and vulnerability. Consequently, the use of nalmefene may be associated with an elevated risk of cardiovascular events.

Opium consumption and long-term outcomes of CABG surgery in patients without modifiable risk factors

Background

The question about the significance of opium consumption as a coronary artery disease (CAD) risk factor still remains open. The present study aimed to evaluate the association between opium consumption and long term outcomes of coronary artery bypass grafting (CABG) in patients without standard modifiable CAD risk factors (SMuRFs; hypertension, diabetes, dyslipidemia, and smoking).

Methods

In this registry-based design, we included 23,688 patients with CAD who underwent isolated CABG between January 2006 to December 2016. Outcomes were compared in two groups; with and without SMuRF. The main outcomes were all-cause mortality, fatal and nonfatal cerebrovascular events (MACCE). Inverse probability weighting (IPW) adjusted Cox's proportional hazards (PH) model was used to evaluate the effect of opium on post-op outcomes.

Results

During 133,593 person-years of follow-up, opium consumption was associated with increased risk of mortality in both patients with and without SMuRFs (weighted Hazard Ratio (HR)s: 1.248 [1.009, 1.574] and 1.410 [1.008, 2.038], respectively). There was no association between opium consumption and fatal and non-fatal MACCE in patients without SMuRF (HR = 1.027 [0.762-1.383], HR 0.700 [0.438-1.118]). Opium consumption was associated with earlier age of CABG in both groups; 2.77 (1.68, 3.85) years in SMuRF-less and 1.70 (1.11, 2.38) years in patients with SMuRFs.

Conclusion

Opium users not only undergo CABG at younger ages but also have a higher rate of mortality regardless of the presence of traditional CAD risk factors. Conversely, the risk of MACCE is only higher in patients with at least one modifiable CAD risk factor.

Opium abuse and stroke in Iran: A systematic review and meta-analysis

Introduction

Opium dependence is a significant health concern in low and middle-income countries, leading to a considerable number of deaths annually. Opium has several detrimental effects on its consumers. Data regarding the impact of opium on stroke are controversial. The objective of this study is to evaluate the association between opium dependence and stroke.

Methods

I conducted a systematic search based on Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines to evaluate the association between opium dependence and stroke. Following the extraction of qualitative findings from included studies, a meta-analysis was performed to assess the pooled estimate of odds ratios (ORs).

Results

Eight and four studies were included in qualitative and quantitative synthesis, respectively. Opium dependence increases the hazard of stroke mortality. Also, opium increases the odds of ischemic stroke by 127% (pooled OR = 2.27, 95% CI: 1.47–3.07).

Conclusion

Opium not only merely increases the odds of being diagnosed with ischemic stroke but also leads to a notable increase in the mortality rate following stroke.

Prevalence of dyslipidemia and its association with opium consumption in the Rafsanjan cohort study

The potential effects of opium consumption on lipid profile remain unquantified. We considered the association between opium use and dyslipidemia. In this cross-sectional study, we used data obtained from the Rafsanjan cohort study, as a part of the prospective epidemiological research studies in IrAN (PERSIAN) with detailed and validated data on opium consumption and selected other exposures. A total of 9932 adults were included in the study. Logistic regression models were used to assess the relationships of opium consumption with the prevalence of dyslipidemia and lipid disorders. In this population, 73.33% had dyslipidemia and the prevalence rates of high TC, high TG, high LDL and low HDL were 54.24%, 47.45%, 34.43% and 11.91% respectively. After adjustment for all confounders, opium users compared with non-users had lower odds ratios (OR) of high TC and high LDL [0.81 (95% confidence interval, CI 0.71–0.92) and 0.80 (95% CI 0.69–0.93) respectively] and greater OR of low HDL [1.30 (95% CI 1.04–1.62)]. Longer duration of opium consumption resulted in lower ORs of high TC, 0.68 (95% CI 0.55–0.84) and high LDL, 0.82 (95% CI 0.67–0.99), and shorter duration of opium consumption resulted in increased odds of low HDL, 1.30 (95% CI 1.02–1.66). High dose of opium consumption was associated with an OR of dyslipidemia of 0.80 (95% CI 0.65–0.97), high TC of 0.80 (95% CI 0.67–0.95), and high LDL of 0.78 (95% CI 0.64–0.96) and low dose of opium consumption, with an OR of low HDL of 1.30 (95% CI 1.02–1.65). In relation to route of consumption, opium smoking was a risk factor for low HDL with an adjusted odds ratio of 1.31 (1.04–1.63). Opium use was associated with selected changes on serum lipid levels, but opium users had higher frequency of cardiovascular disease history.

Codeine exerts cardiorenal injury via upregulation of adenine deaminase/xanthine oxidase and caspase 3 signaling

AIMS

Codeine treatment has been shown to be associated with glucolipid deregulation, though data reporting this are inconsistent and the mechanisms are not well understood. Perturbation of glutathione-dependent antioxidant defense and adenosine deaminase (ADA)/xanthine oxidase (XO) signaling has been implicated in the pathogenesis of cardiometabolic disorders. We thus, hypothesized that depletion of glutathione contents and upregulation of ADA/XO are involved in codeine-induced glucolipid deregulation. The present study also investigated whether or not codeine administration would induce genotoxicity and apoptosis in cardiac and renal tissues.

MATERIALS AND METHODS

Male New Zealand rabbits received per os distilled water or codeine, either in low dose (4 mg/kg) or high dose (10 mg/kg) for 6 weeks.

KEY FINDINGS

Codeine treatment led to reduced absolute and relative cardiac and renal mass independent of body weight change, increased blood glucose, total cholesterol (TC), triglycerides (TG), and low-density lipoprotein (LDL-C), as well as increased atherogenic indices and triglyceride-glucose index (TyG). Codeine administration significantly increased markers of cardiac and renal injury, as well as impaired cardiorenal functions. Codeine treatment also resulted in increased cardiac and renal malondialdehyde, Advanced Glycation Endproducts (AGE) and 8-hydroxydeoxyguanosine (8-OH-dG), and myeloperoxidase (MPO), ADA, XO, and caspase 3 activities. These observations were accompanied by impaired activities of cardiac and renal proton pumps.

SIGNIFICANCE

Findings of this study demonstrate that upregulation of ADA/XO and caspase 3 signaling are, at least partly, contributory to the glucolipid deregulation and cardiorenal injury induced by codeine.

Repeated Administration of Clinical Doses of Tramadol and Tapentadol Causes Hepato- and Nephrotoxic Effects in Wistar Rats

Tramadol and tapentadol are fully synthetic and extensively used analgesic opioids, presenting enhanced therapeutic and safety profiles as compared with their peers. However, reports of adverse reactions, intoxications and fatalities have been increasing. Information regarding the molecular, biochemical, and histological alterations underlying their toxicological potential is missing, particularly for tapentadol, owing to its more recent market authorization. Considering the paramount importance of liver and kidney for the metabolism and excretion of both opioids, these organs are especially susceptible to toxicological damage. In the present study, we aimed to characterize the putative hepatic and renal deleterious effects of repeated exposure to therapeutic doses of tramadol and tapentadol, using an in vivo animal model. Male Wistar rats were randomly divided into six experimental groups, composed of six animals each, which received daily single intraperitoneal injections of 10, 25 or 50 mg/kg tramadol or tapentadol (a low, standard analgesic dose, an intermediate dose and the maximum recommended daily dose, respectively). An additional control group was injected with normal saline. Following 14 consecutive days of administration, serum, urine and liver and kidney tissue samples were processed for biochemical, metabolic and histological analysis. Repeated administration of therapeutic doses of both opioids led to: (i) increased lipid and protein oxidation in liver and kidney, as well as to decreased total liver antioxidant capacity; (ii) decreased serum albumin, urea, butyrylcholinesterase and complement C3 and C4 levels, denoting liver synthesis impairment; (iii) elevated serum activity of liver enzymes, such as alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and γ-glutamyl transpeptidase, as well as lipid profile alterations, also reflecting hepatobiliary commitment; (iv) derangement of iron metabolism, as shown through increases in serum iron, ferritin, haptoglobin and heme oxygenase-1 levels. In turn, elevated serum cystatin C, decreased urine creatinine output and increased urine microalbumin levels were detected upon exposure to tapentadol only, while increased serum amylase and urine N-acetyl-β-D-glucosaminidase activities were observed for both opioids. Collectively, these results are compatible with kidney injury. Changes were also found in the expression levels of liver- and kidney-specific toxicity biomarker genes, upon exposure to tramadol and tapentadol, correlating well with alterations in lipid profile, iron metabolism and glomerular and tubular function. Histopathological analysis evidenced sinusoidal dilatation, microsteatosis, mononuclear cell infiltrates, glomerular and tubular disorganization, and increased Bowman's spaces. Although some findings are more pronounced upon tapentadol exposure, our study shows that, when compared with acute exposure, prolonged administration of both opioids smooths the differences between their toxicological effects, and that these occur at lower doses within the therapeutic range.

Lipid profile of regular kratom (Mitragyna speciosa Korth.) users in the community setting

Background and aim

Kratom, or Mitragyna speciosa Korth., is a tropical plant that has been reported to exhibit opioid-like effects. Although opioids have been demonstrated to alter the lipid profile of regular users, data on the lipid-altering effects of kratom are scarce. This study aimed to compare the fasting lipid profile of regular kratom users to that of healthy subjects who do not use kratom. It also determined the association between various characteristics of kratom users and the serum triglycerides, total cholesterol, low-density lipoprotein (LDL), and high-density lipoprotein (HDL) levels of regular kratom users.

Methods

A total of 200 participants (n = 100 kratom users and n = 100 healthy subjects who do not use kratom) were recruited for this analytical cross-sectional study. Data on sociodemographic status, kratom use characteristics, cigarette smoking, physical activity, body mass index (BMI), fasting serum lipid profile, and liver function were collected from all participants.

Results

The liver parameters of the study participants were within normal range. The serum total cholesterol and LDL of kratom users were significantly lower than those of healthy subjects who do not use kratom. There were no significant differences in the serum triglyceride and HDL levels. However, higher average daily frequency of kratom use and increasing age were associated with increased serum total cholesterol among kratom users. Other kratom use characteristics such as age of first kratom intake, duration of kratom use, and quantity of daily kratom intake were not associated with increased serum triglyceride, total cholesterol, LDL, and HDL levels.

Conclusions

Our findings suggest regular kratom consumption was not linked to elevated serum lipids, except when there is a higher frequency of daily kratom intake. However, the study was limited by the small sample size, and hence a more comprehensive study with larger sample size is warranted to confirm the findings.

Gut microbiota density influences host physiology and is shaped by host and microbial factors

To identify factors that regulate gut microbiota density and the impact of varied microbiota density on health, we assayed this fundamental ecosystem property in fecal samples across mammals, human disease, and therapeutic interventions. Physiologic features of the host (carrying capacity) and the fitness of the gut microbiota shape microbiota density. Therapeutic manipulation of microbiota density in mice altered host metabolic and immune homeostasis. In humans, gut microbiota density was reduced in Crohn's disease, ulcerative colitis, and ileal pouch-anal anastomosis. The gut microbiota in recurrent Clostridium difficile infection had lower density and reduced fitness that were restored by fecal microbiota transplantation. Understanding the interplay between microbiota and disease in terms of microbiota density, host carrying capacity, and microbiota fitness provide new insights into microbiome structure and microbiome targeted therapeutics.

Editorial note

This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter).

Cardiovascular complications and related risk factors underlying opium consumption

Opium is considered as the second most abused addictive compound in worldwide. It seems that one of the causes for common consumption of opium in many countries is a traditional belief, even among medical personnel, through which opium might have advantageous influences on cardiovascular events and be beneficial in controlling hypertension, dyslipidemia, and diabetes. According to several investigations, it is thought that opium not only has no beneficial effects on cardiovascular events, but it might have deleterious influences on these settings. As a result, people need to be trained with regard to the adverse effects of opium on cardiovascular events. In this review, we try to go through the understanding of the effects of opium cardiovascular disorders and related complications such as blood pressure, blood sugar, lipid circumstances, and finally atherosclerosis.

Naltrexone changes the expression of lipid metabolism-related proteins in the endoplasmic reticulum stress induced hepatic steatosis in mice

Endoplasmic reticulum (ER) stress is closely associated with several chronic diseases such as obesity, atherosclerosis, type 2 diabetes, and hepatic steatosis. Steatosis in hepatocytes may also lead to disorders such as nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH), fibrosis, and possibly cirrhosis. Opioid peptides are involved in triglyceride and cholesterol dysregulation. Naltrexone also attenuates ER stress induced hepatic steatosis in mice. In this study, we evaluated the effects of naltrexone on the expression of lipid metabolism-related nuclear factors and enzymes in the ER stress induced hepatic steatosis. C57/BL6 mice received saline, DMSO and naltrexone as control groups. In a fourth group, ER stress was induced by tunicamycin (TM) injection and in the last group, naltrexone was given before TM administration. Histopathological evaluations, real-time RT-PCR and western blot were performed. We found that GRP78, IRE1α, PERK and ATF6 gene expression and steatosis significantly reduced in naltrexone treated animals. Naltrexone alleviated the gene and protein expression of SREBP1c. Expression of ACAT1, apolipoprotein B (ApoB) and PPARα also increased after naltrexone treatment. In conclusion, this study, for the first time, shows that naltrexone has a considerable role in attenuation of ER stress-induced liver injury.

The Impact of Opium Consumption on Blood Glucose, Serum Lipids and Blood Pressure, and Related Mechanisms

Aim: Substance abuse has become a universal crisis in our modern age. Among illegal substances, opium and its derivatives have been ranked second in terms of usage after cannabis in the world. In many Asian regions, the use of opium enjoys a high social acceptance; hence, some common people and even medical practitioners believe that opium lowers blood glucose and pressure and treat dyslipidemia. How much this belief is scientifically justified?

Method: The results of available studies on both humans and animals searched in different search engines up to mid-2016 were integrated (78 articles). Upon the findings we try to offer a more transparent picture of the effects of opium on the mentioned factors along with the probable underlying mechanisms of its action.

Results: Taken together, a variety of evidences suggest that the consumption of opium has no scientific justification for amendment of these biochemical variables. The mechanisms proposed so far for the action of opium in the three above disorders are summarized at the end of the article. Short term effects seems to be mostly mediated through central nervous system (neural and hormonal mechanisms), but long term effects are often due to the structural and functional alterations in some body organs.

Conclusion: Although opium may temporarily reduce blood pressure, but it increases blood glucose and most of blood lipids. Moreover its long term use has negative impacts and thus it aggravates diabetes, dyslipidemia and hypertension. Accordingly, it is necessary to inform societies about the potential disadvantages of unauthorized opium consumption.

Naltrexone attenuates endoplasmic reticulum stress induced hepatic injury in mice

Endoplasmic reticulum (ER) stress provides abnormalities in insulin action, inflammatory responses, lipoprotein B100 degradation and hepatic lipogenesis. Excess accumulation of triglyceride in hepatocytes may also lead to disorders such as non-alcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH). Opioid peptides are involved in triglyceride and cholesterol dysregulation, inflammation and cell death. In this study, we evaluated Naltrexone effects on ER stress induced liver injury. To do so, C57/BL6 mice received saline, DMSO and Naltrexone, as control groups. ER stress was induced by tunicamycin (TM) injection. Naltrexone was given before TM administration. Liver blood flow and biochemical serum analysis were measured. Histopathological evaluations, TNF-α measurement and Real-time RT-PCR were also performed. TM challenge provokes steatosis, cellular ballooning and lobular inflammation which significantly reduced in Naltrexone treated animals. ALT, AST and TNF-α increased in the TM group and improved in the Naltrexone plus TM group. Triglyceride and cholesterol levels decreased in TM treated mice with no increase in Naltrexone treated animals. In the Naltrexone plus TM group, gene expression of Bax/Bcl-2 ratio and caspase3 significantly lowered compared with the TM group. In this study, we found that Naltrexone had a notable alleviating role in ER stress induced steatosis and liver injury.

Effects of opium consumption on cardiometabolic diseases

Opium is the second-most-commonly abused substance (after tobacco) in developing countries of the Middle East region, and in many Asian nations. One of the reasons for the high prevalence of opium abuse in these countries is a traditional belief among Eastern people, even including some medical staff, that opium might have beneficial effects on cardiovascular health and in the control of diabetes mellitus, hypertension, and dyslipidaemia. In this Perspectives article, we summarize the current understanding of the pharmacotoxicology of opium and its specific effects on glycaemic control, blood pressure, lipid profile, and atherosclerosis. On the basis of the available evidence, we believe not only that opium has no ameliorating effect on cardiovascular diseases, but also that the use of this drug might have adverse effects on these conditions. Therefore, people should be educated about the hazardous effects of opium consumption on cardiometabolic diseases.

Morphine withdrawal stress modulates lipopolysaccharide-induced interleukin 12 p40 (IL-12p40) expression by activating extracellular signal-regulated kinase 1/2, which is further potentiated by glucocorticoids

Withdrawal stress is a common occurrence in opioid users, yet very few studies have examined the effects of morphine withdrawal (MW) on immune functioning or the role of glucocorticoids in MW-induced immunomodulation. This study investigated for the first time the role of glucocorticoids in MW modulation of LPS-induced IL-12p40, a key cytokine playing a pivotal role in immunoprotection. Using WT and μ-opioid receptor knock-out mice, we show that MW in vivo significantly attenuated LPS-induced IL-12p40 mRNA and protein expression. The role of glucocorticoids in MW modulation of IL-12p40 was investigated using a murine macrophage cell line, CRL2019, in an in vitro MW model. Interestingly, MW alone in the absence of glucocorticoids resulted in a significant reduction in IL-12p40 promoter activity and mRNA and protein expression. EMSA revealed a concurrent decrease in consensus binding to transcription factors NFκB, Activator Protein-1, and CCAAT/enhancer-binding protein and Western blot analysis demonstrated a significant activation of LPS-induced ERK1/2 phosphorylation. Interestingly, although glucocorticoid treatment alone also modulated these transcription factors and ERK1/2 activation, the addition of glucocorticoids to MW samples resulted in a greater than additive reduction in the transcription factors and significant hyperactivation of LPS-induced ERK1/2 phosphorylation. ERK inhibitors reversed MW and MW plus corticosterone inhibition of LPS-induced IL-12p40. The potentiating effects of glucocorticoids were non-genomic because nuclear translocation of glucocorticoid receptor was not significantly different between MW and corticosterone treatment. This study demonstrates for the first time that MW and glucocorticoids independently modulate IL-12p40 production through a mechanism involving ERK1/2 hyperactivation and that glucocorticoids can significantly augment MW-induced inhibition of IL-12p40.

Intensity of pain and biochemical changes in blood plasma in spinal cord trauma

STUDY DESIGN

Cross-sectional, observational and longitudinal.

OBJECTIVES

The aim of the study was to analyze the relationship between pain intensity, plasma lipids and severity of spinal cord injuries in patients with paraplegia (n = 11), tetraplegia (n = 16) and polytrauma (n = 15). We concentrated on the hospitalization period immediately following injury.

METHODS

Pain intensity was assessed on a visual analog scale immediately after patients were transported to hospital, again 14 days after injury and before discharge from hospital. Blood samples were also obtained at these same times. We measured following biochemical parameters: total protein, albumin, total cholesterol, HDL cholesterol, LDL cholesterol, triglycerides, glycemia, and C-reactive protein. Data were analyzed with respect to type of injury, state of unconsciousness immediately after injury, hemorrhage, measure of liability (self-inflicted injuries vs casualties), cause of the accident and pre-injury cholesterol levels.

RESULTS

On the day of injury, pain intensity correlated positively with HDL cholesterol (r = 0.48, P = 0.04); on the day of discharge from hospital, pain intensity correlated positively with blood glucose levels (r = 0.67, P = 0.0002). Diagnostic subgroups did not differ either in pain intensity or in pain dynamics during hospitalization. Total cholesterol level was lowest in patients with polytrauma. In all patients, the lowest total cholesterol level was observed immediately after injury. HDL cholesterol was highest after injury.

CONCLUSION

After spinal cord injury, lower total cholesterol levels reflected more serious trauma intensity and HDL cholesterol predicted more intensive pain. Subjects responsible for their own injuries suffered less intensive pain than those who were not responsible for their injuries.

Effect of opium addiction on lipid profile and atherosclerosis formation in hypercholesterolemic rabbits

In some Asian and Middle Eastern societies, opium consumption has traditionally been regarded as a way to lower blood lipids and to prevent heart diseases. This could eventually lead to addiction. In this study, the effect of oral opium consumption on serum lipids and atherogenesis in rabbits was investigated. Twenty-eight male New Zealand white rabbits were divided into control, hypercholesterolemic, addicted, and hypercholesterolemic-addicted groups and were studied for 3 months. Serum lipid profile was determined at the beginning of the study and at 1 month intervals thereafter. At the end of the study period, aortic plaque formation was assessed. Compared with control, in the hypercholesterolemic and hypercholesterolemic-addicted groups, cholesterol, triglycerides, and low-density lipoprotein cholesterol levels were significantly increased (P<0.01). The increases in lipids and lesion areas in the aorta were higher in hypercholesterolemic-addicted than hypercholesterolemic group (P<0.05). Our findings suggest that opium consumption can have aggravating effects in atherosclerosis formation related with hypercholesterolemia, mainly affecting lipid profile.

Nicotine and stress: effect on sex hormones and lipid profile in female rats

This work aimed to study the changes in sex hormones and lipid profile in adult female albino rats subjected to treatment with nicotine (N), immobilization stress (S), or their combinations (N+S). These treatments were applied either for one day (T1) or daily for 10 days (T10), after which rats in the estrus stage were used for the determination of plasma corticosterone (CS), serum sex hormones as progesterone (P), estrogen (E), FSH, LH and serum lipid profile including total cholesterol (TC), HDL-C, LDL-C, triacylglycerol (TG) and non esterified fatty acids (NEFA). It was clear that either N or S raised plasma CS and serum P levels in both the treatment regimens and that N+S induced a higher level of these hormones compared to each treatment alone. Serum E level was only elevated during T10 regimen only. An increase in serum LH level was only observed after a single exposure to either N or S, however their combination abolished the stimulatory effect induced by each treatment alone. Serum FSH was not altered by exposure to either N or S alone in both regimens, but in the T10 regimen their combination significantly lowered FSH level. Regarding the effect on serum lipid profile, serum TC was increased in all T10 regimen groups. LDL-C was increased by N+S treatment in both regimens, however no change in HDL-C level was observed in all groups. Serum NEFA was increased in all the treated groups during T10 regimen, while in the T1 regimen NEFA level was only elevated by the combination N+S. Serum TG was insignificantly altered in all the treated groups. The observed changes in the lipid pattern were attributed to the alterations occurred in CS and female sex hormones that caused by N, S or their combinations.

The effect of L-tyrosine on some anti-nociceptive and non-nociceptive actions of morphine in mice

1. This work examines the effect of L-tyrosine on the antinociceptive and non-nociceptive actions of morphine in mice. The antinociceptive action was measured using the hot plate method, and the non-nociceptive actions included the effect on concentrations of glucose, cholesterol and triglycerides in serum or blood, and the effect on gastrointestinal transit time (GITT) and rectal temperature. 2. L-tyrosine (25, 50, 100 and 200 mg/kg), subcutaneously (s.c.) dose-dependently potentiated the antinociceptive action of morphine (5 mg/kg, s.c.). L-tyrosine alone did not produce significant antinociceptive action, nor did it affect any of the other non-nociceptive actions measured. 3. Acute administration of morphine (5, 10 and 20 mg/kg) produced dose-dependent increases in blood glucose concentration which were insignificantly potentiated by L-tyrosine (25-200 mg/kg) when given together with morphine. Morphine produced dose-dependent and significant decrease in serum triglycerides concentrations, an effect which was not influenced by L-tyrosine treatment. Serum cholesterol was not affected by treatment with morphine, either alone or when given with L-tyrosine. 4. Morphine produced dose-dependent and significant decreases in GITT which was not affected with L-tyrosine.

Restraint stress in biomedical research: an update

Since the publication of our initial review of restraint stress in 1986, much work has continued with this technique, either as a tool for the investigation of other pharmacological, physiological, or pathologic phenomena or with restraint stress itself serving as the object of the study. As we noted in 1986, the major use of restraint has been for the induction of stress responses in animals and, more specifically, for the investigation of drug effects, particularly as they affect typical stress-related pathology--gastrointestinal, neuroendocrine, and immunological agents have been extensively studied. In compiling this update on restraint stress and its effects, we noted an increasing emphasis on central nervous system mechanisms in peripheral disease, especially gastrointestinal disease. In particular, many CNS-active agents have been tested for their effects on gastric and duodenal lesion formation and gastric secretion, including antidepressants, antipsychotics, anxiolytics, noradrenergic, serotonergic, dopaminergic, and peptidergic compounds. Some of these agents are especially active in the gastrointestinal tract even when administered centrally, further solidifying the concept of a brain-gut axis. The present update includes studies of: methods and procedures, pre-restraint manipulations, post-restraint/healing effects, and drug effects. In addition, a current bibliography of reports that have employed restraint is included.

Enhanced lithogenicity of bile following chronic morphine administration to female guinea pigs

Acute and chronic opiate exposure impairs the emptying of bile from the gallbladder. In this study, the effects of a 4-day morphine regimen on bile composition were examined. Bile acids and phospholipids concentration of bile obtained from the gallbladder of female morphine-treated (MT) guinea pigs were reduced by 60% and 80% respectively, resulting in a highly lithogenic bile. Concentrations of bile acids and phospholipids of spontaneously secreted bile were not reduced. However, the lithogenicity of the hepatic bile in MT animals was still increased because of a 10 fold elevation in cholesterol concentration. Ratios of solute concentrations of stored and freshly secreted bile indicated that morphine also impaired the ability of the gallbladder to concentrate bile. Thus chronic morphine exposure increased bile lithogenicity by increasing cholesterol content and also by diluting the bile in the gallbladder. These alterations and the previously described biliary stasis indicates that chronic opiate and endogenous opioid exposure should facilitate gallstone formation.

Effects of chronic morphine on biliary tract responses to cholecystokinin-octapeptide in male guinea pigs

Opioid peptides share the spasmogenic action of acutely administered morphine on the sphincter of Oddi. In this study, gallbladder function was assessed following chronic opioid administration. Implantation of morphine pellets (400 mg) in male guinea pigs depressed cholecystokinin-octapeptide(CCK)-induced emptying of gallbladder bile (monitored via a duodenal cannula). Gallbladder muscle strips, isolated from the morphine treated animals, showed depressed contractile responses to CCK. This antagonism was non-specific and indirectly mediated, as ACh contractions were also depressed, whereas CCK-induced contractions of gallbladder strips from untreated animals were unaffected by direct exposure to morphine (3 x 10(-6)M). The depression of CCK stimulation of bile flow by chronic morphine administration in male guinea pigs suggests that chronic exposure to opioids can impede gallbladder emptying.

Endogenous opiates: 1988

This paper is the eleventh installment in our annual review of the research during the past year involving the endogenous opiate system. It is concerned with nonanalgesic and behavioral studies of the opiate peptides that were published during 1988. The specific topics this year include stress; tolerance and dependence; eating; drinking; gastrointestinal, renal, and hepatic functions; mental illness; learning, memory, and reward; cardiovascular responses; respiration and thermoregulation; seizures and other neurological disorders; electrical activity; locomotor activity; sex, pregnancy, and development; immunology and cancer; and other behavior.