Amphetamine, an appetite suppressant, decreases neuropeptide Y immunoreactivity in rat hypothalamic paraventriculum

Urinary retention concomitant with methamphetamine use: a case report

Background

Urinary retention is a condition in which impaired emptying of the bladder results in postvoid residual urine. It can be acute or chronic urinary retention. There have been only scattered case studies that have described urinary retention resulting from methamphetamine use. This case report is aimed at raising awareness about methamphetamine abuse as an important factor in the aetiological considerations when evaluating cases of urinary retention among healthy younger age groups.

Case presentation

We report a patient who had acute urinary retention after brief amphetamine use. A 26-year-old Nigerian man presented at the emergency room on account of an inability to pass urine and lower abdominal pain. Before this incident, the patient reported a recent ingestion of amphetamine to achieve weight reduction and a fit body. A week after use, he started to experience difficulty passing out urine hence necessitating a visit to the emergency department. After a brief assessment, physical examination revealed a man in painful distress with mild suprapubic fullness. He had a successful passage of a urethral catheter for continuous bladder drainage with dramatic improvement in his symptoms. He was subsequently discontinued on methamphetamine use and referred to a urologist for further evaluation.

Conclusion

Most cases of urinary retention are diagnosed clinically and are rarely missed. But because urinary retention is associated with a wide range of aetiological factors, clinicians need to be aware of the effects of certain drugs in the aetiology of urinary retention. In the management of a case of urinary retention in the younger age group, clinicians should enquire about a history of drug use, the drug of particular interest being methamphetamine, and also employ the use of urodynamic studies in the evaluation of such cases.

Critical View on the Usage of Ribavirin in Already Existing Psychostimulant-Use Disorder

Substance-use disorder represents a frequently hidden non-communicable chronic disease. Patients with intravenous drug addiction are at high risk of direct exposure to a variety of viral infections and are considered to be the largest subpopulation infected with the hepatitis C virus. Ribavirin is a synthetic nucleoside analog that has been used as an integral component of hepatitis C therapy. However, ribavirin medication is quite often associated with pronounced psychiatric adverse effects. It is not well understood to what extent ribavirin per se contributes to changes in drug-related neurobehavioral disturbances, especially in the case of psychostimulant drugs, such as amphetamine. It is now well-known that repeated amphetamine usage produces psychosis in humans and behavioral sensitization in animals. On the other hand, ribavirin has an affinity for adenosine A1 receptors that antagonistically modulate the activity of dopamine D1 receptors, which play a critical role in the development of behavioral sensitization. This review will focus on the current knowledge of neurochemical/ neurobiological changes that exist in the psychostimulant drug-addicted brain itself and the antipsychotic-like efficiency of adenosine agonists. Particular attention will be paid to the potential side effects of ribavirin therapy, and the opportunities and challenges related to its application in already existing psychostimulant-use disorder.

Gut Peptide Agonism in the Treatment of Obesity and Diabetes

Obesity is a global healthcare challenge that gives rise to devastating diseases such as the metabolic syndrome, type-2 diabetes (T2D), and a variety of cardiovascular diseases. The escalating prevalence of obesity has led to an increased interest in pharmacological options to counteract excess weight gain. Gastrointestinal hormones such as glucagon, amylin, and glucagon-like peptide-1 (GLP-1) are well recognized for influencing food intake and satiety, but the therapeutic potential of these native peptides is overall limited by a short half-life and an often dose-dependent appearance of unwanted effects. Recent clinical success of chemically optimized GLP-1 mimetics with improved pharmacokinetics and sustained action has propelled pharmacological interest in using bioengineered gut hormones to treat obesity and diabetes. In this article, we summarize the basic biology and signaling mechanisms of selected gut peptides and discuss how they regulate systemic energy and glucose metabolism. Subsequently, we focus on the design and evaluation of unimolecular drugs that combine the beneficial effects of selected gut hormones into a single entity to optimize the beneficial impact on systems metabolism. © 2020 American Physiological Society. Compr Physiol 10:99-124, 2020.

Comparison of Effects of Light Anesthetics, Diethyl Ether and Carbon Dioxide, on Hypothalamic Paraventricular Nucleus D1 and D2 Dopamine Receptors- and Glucosensitive Neurons-Induced Food Intake in Fasted Conscious Rats

Introduction

Carbon Dioxide (CO₂) and diethyl ether are used as light anesthetics. However, experimental data about their side effects are scarce. In addition, in all our previous works on regulatory mechanisms of hypothalamus during food intake, including the effect of Paraventricular Nucleus (PVN) D₁ and D₂ dopamine receptors and glucosensitive neurons, the drug injections were performed under brief diethyl ether anesthesia. In the current study, we tested the hypothesis which postulates that CO₂ and diethyl ether as light anesthetic agents affect the stimulatory effect of PVN dopamine receptors and glucosensitive neurons in feeding behavior.

Methods

Male Wistar rats were implanted with guide cannula directed to their PVN. Glucose (0.8 μg), SKF38393 (D₁ agonist, 0.5 μg), quinpirole (D₂ agonist, 0.3 μg) and saline (0.3 μL) were microinjected into the PVN and food intake was measured over 1 hour.

Results

Our results showed that CO₂ but not diethyl ether decreased food intake compared to intact animals. The PVN injections of glucose, SKF38393, and quinpirole increased food intake under brief diethyl ether anesthesia. In contrast, the PVN microinjected glucose-induced and dopamine receptor agonists-induced food intake were inhibited under light CO₂ anesthesia.

Conclusion

Our results suggest that brief exposure to CO₂ and diethyl ether as light anesthetic agents may affect PVN glucosensing neurons-induced and dopamine receptors-induced food intake in fasted rats.

Role of hypothalamic leptin-LepRb signaling in NPY-CART-mediated appetite suppression in amphetamine-treated rats

Leptin is an adipose tissue hormone which plays an important role in regulating energy homeostasis. Amphetamine (AMPH) is a drug of appetite suppressant, which exerts its effect by decreasing the expression of hypothalamic neuropeptide Y (NPY) and increasing that of cocaine- and amphetamine-regulated transcript (CART). This study investigated whether leptin, the leptin receptor (LepRb) and the signal transducer and activator of transcription-3 (STAT3) were involved in NPY/CART-mediated appetite suppression in AMPH-treated rats. Rats were given AMPH daily for four days, and changes in the levels of blood leptin and hypothalamic NPY, CART, LepRb, Janus kinases 2 (JAK2), and STAT3 were assessed and compared. During the AMPH treatment, blood leptin levels and hypothalamic NPY expression decreased, with the largest reduction observed on Day 2. By contrast, the expression of hypothalamic CART, LepRb, JAK2, and STAT3 increased, with the maximum response on Day 2. Furthermore, the binding activity of pSTAT3/DNA increased and was expressed in similar pattern to that of CART, LepRb, and JAK2. An intracerebroventricular infusion of NPY antisense 60min prior to AMPH treatment increased the levels of leptin, as well as the expression in LepRb, JAK2, and CART, whereas an infusion of STAT3 antisense decreased these levels and the expression of these parameters. The results suggest that blood leptin and hypothalamic LepRb-JAK2-STAT3 signaling involved in NPY-CART-regulated appetite suppression in AMPH-treated rats. The findings may aid understanding the role of leptin-LepRb during the treatment of anorectic drugs.

Knockdown of the transcript of ERK in the brain modulates hypothalamic neuropeptide-mediated appetite control in amphetamine-treated rats

BACKGROUND AND PURPOSE

Amphetamine is a releaser of dopamine stored in synaptic terminals, which can suppress appetite by changing the expression levels of neuropeptide Y (NPY) and proopiomelanocortin (POMC) in the hypothalamus. This study explored whether ERKs are involved in appetite control mediated by cAMP response element binding protein (CREB), NPY and POMC in amphetamine-treated rats.

EXPERIMENTAL APPROACH

Rats were given amphetamine for 4 days, and changes in feeding behaviour and expression levels of phosphorylated-ERK (pERK), pCREB, NPY and melanocortin MC₃ receptors were examined and compared.

KEY RESULTS

Following amphetamine treatment, food intake, body weight and NPY expression decreased, whereas the expression of pERK, pCREB, MC₃ receptors and pCREB/DNA binding activity increased. In amphetamine-treated rats, both cerebral ERK knockdown and pretreatment with a peripheral dopamine receptor antagonist decreased NPY but increased pERK, pCREB and MC₃ receptor expression. Moreover, the immunofluorescence of hypothalamic pERK increased following amphetamine treatment.

CONCLUSIONS AND IMPLICATIONS

These results suggest that ERK/CREB signalling participates in the effects mediated by dopamine receptor/NPY/POMC on appetite control in rats treated with amphetamine. These findings advance the knowledge on the involvement of ERK/CREB signalling in the reciprocal regulation by NPY and POMC of appetite after amphetamine treatment.

Role of paraventricular hypothalamic dopaminergic D1 receptors in food intake regulation of food-deprived rats

Dopaminergic neurons play an important role on central regulatory mechanisms of feeding behavior. Dopamine receptors are distributed within the hypothalamus and densely localized in the paraventricular hypothalamic nucleus (PVN). From these ideas we postulated that PVN D₁ receptors may play a role in regulating the food intake behavioral process. In this paper, we considered the effects of SKF38393, a D₁ receptor agonist, and the D₁ receptor antagonist (SCH23390), on food intake of conscious rats deprived of food for 24h. Our findings revealed that intraparaventricular injections of SKF383993 (0.3-5µg) stimulated food intake behavior in a dose dependent manner. This stimulatory effect of SKF3833 persisted over 2h of the monitoring period. The PVN injections of D₁ receptor antagonist were associated with dose-dependent inhibition of food intake. SCH23390 (0.01µg) was also administered 5min before intraparaventricular injection of SKF3833. The results showed that SCH23390 suppressed stimulated food intake induced by SKF38393 (1.2µg). In conclusion, endogenous dopamine impact PVN D₁ receptors and may be a factor in regulating the food intake behavioral process.

Role of oxidative stress in disrupting the function of negative glucocorticoid response element in daily amphetamine-treated rats

Amphetamine (AMPH)-induced appetite suppression is associated with changes in hypothalamic reactive oxygen species (ROS), antioxidants, neuropeptides, and plasma glucocorticoid. This study explored whether ROS and glucocorticoid response element (GRE), which is the promoter site of corticotropin-releasing hormone (CRH) gene, participated in neuropeptides-mediated appetite control. Rats were treated daily with AMPH for four days, and changes in food intake, plasma glucocorticoid and expression levels of hypothalamic neuropeptide Y (NPY), proopiomelanocortin (POMC), superoxide dismutase (SOD), CRH, and glucocorticoid receptor (GR) were examined and compared. Results showed that food intake decreased and NPY gene down-regulated, while POMC, SOD, and CRH gene up-regulated during AMPH treatment. GR and GRE-DNA bindings were disrupted on Day 1 and Day 2 when glucocorticoid levels were still high. Pretreatment with GR inhibitor or ROS scavenger modulated mRNA levels in NPY, POMC, SOD and CRH in AMPH-treated rats. We suggest that disruptions of negative GRE (nGRE) on Day 1 and Day 2 are associated with an increase in oxidative stress during the regulation of NPY/POMC-mediated appetite control in AMPH-treated rats. These results advance the understanding of molecular mechanism in regulating AMPH-mediated appetite suppression.

Involvement of oxidative stress in the regulation of NPY/CART-mediated appetite control in amphetamine-treated rats

Amphetamine (AMPH) treatment can suppress appetite and increase oxidative stress in the brain. AMPH-induced appetite suppression is associated with the regulation of neuropeptide Y (NPY) and cocaine- and amphetamine-regulated transcript (CART) in the hypothalamus. The present study explored whether antioxidants, including glutathione S-transferase (GST) and glutathione peroxidase (GP), were involved in this NPY/CART-mediated appetite control. Rats were treated daily with AMPH for four days. Changes in food intake and expression levels of hypothalamic NPY, CART, GST, and GP were examined and compared. Results showed that, in AMPH-treated rats, (1) food intake and NPY expression decreased, while CART, GST, and GP expression increased; (2) NPY knockdown in the brain enhanced the decrease in NPY and the increases in CART, GST, and GP expression; and (3) central inhibition of reactive oxygen species production decreased GST and GP and modulated AMPH anorexia and the expression levels of NPY and CART. The present results suggest that oxidative stress in the brain participates in regulating NPY/CART-mediated appetite control in AMPH-treated rats. These results may advance the knowledge regarding the molecular mechanism of AMPH-evoked or NPY/CART-mediated appetite suppression.

Khat use and appetite: an overview and comparison of amphetamine, khat and cathinone

ETHNOPHARMACOLOGICAL RELEVANCE

To understand the role of khat (Catha edulis) use on the aberrations in appetite and weight which are common comorbidities for khat and other amphetamine users.

MATERIALS AND METHODS

We provide a comprehensive overview and conceptual summary of the historical cultural use of khat as a natural stimulant and describe the similarities and differences between cathinone (the main psychoactive constituent of khat) and amphetamine highlighting the limited literature on the neurophysiology of appetite and subsequent weight effects of khat.

RESULTS

Animal and some human studies indicate that khat produces appetite suppression, although little is known about mechanisms of this effect. Both direct and indirect effects of khat stem from multiple factors including behavioral, chemical and neurophysiological effects on appetite and metabolism. Classic and newly identified appetite hormones have not been explored sufficiently in the study of appetite and khat use. Unique methodological challenges and opportunities are encountered when examining effects of khat and cathinone including khat-specific medical comorbidities, unique route of administration, differential patterns of behavioral effects relative to amphetamines and the nascent state of our understanding of the neurobiology of this drug.

CONCLUSION

A considerable amount of work remains in the study of the appetite effects of khat chewing and outline a program of research that could inform our understanding of this natural amphetamine׳s appetite effects and help prepare health care workers for the unique health effects of this drug.

Involvement of hypothalamic PI3K-STAT3 signalling in regulating appetite suppression mediated by amphetamine

BACKGROUND AND PURPOSE

Appetite suppression induced by amphetamine has been attributed to its inhibition of neuropeptide Y (NPY) neurons and activation of pro-opiomelanocortin (POMC) neurons in the hypothalamus. This study examined whether STAT3 was involved in these actions of amphetamine.

EXPERIMENTAL APPROACH

Rats were given amphetamine daily for 4 days. Changes in the expression of NPY, POMC, melanocortin MC3 receptors, PI3K and STAT3 in the hypothalamus were assessed by RT-PCR and Western blotting. Antisense oligonucleotides to STAT3 were also used.

KEY RESULTS

Expression of NPY decreased with a maximum effect day 2 of amphetamine treatment. Expression of POMC, MC3 receptors, PI3K and STAT3 increased with a maximum response on day 2. Moreover, phosphorylation of STAT3 and its DNA binding activity increased and was expressed in a similar pattern. Infusion (i.c.v.) of STAT3 antisense at 60 min before amphetamine treatment, partly blocked amphetamine-induced anorexia and modulated expression of NPY, POMC, MC3 receptors and PI3K, indicating the involvement of STAT3 in amphetamine-treated rats.

CONCLUSIONS AND IMPLICATIONS

Hypothalamic PI3K-STAT3 signalling participated in the regulation of NPY- and POMC-mediated appetite suppression. These findings may contribute to a better understanding of anorectic drugs.

The effects of dose and repeated administration on the longer-term hypophagia produced by amphetamine in rats

Rats are hypophagic approximately 1-3 and 13-27h after receiving amphetamine (2.0mg/kg). This study examined how these short- and longer-term phases of hypophagia were affected by repeated administration of different amphetamine doses. Throughout eight five-day tests, the rats could lever press for food pellets for 1-hour periods beginning every three hours. On test day 1, the rats were treated with saline, and on test day 3, they were treated with a dose of amphetamine. Across tests, for one group, treatment on day 3 alternated between 0.0 (saline) and 0.5mg/kg amphetamine; for a second, group treatment on day 3 alternated between 1.0 and 2.0mg/kg amphetamine; and for a third group, treatment on day 3 was always 1.0mg/kg amphetamine. The patterns of food intake following day 1 saline and day 3 treatment were compared. Short-term food intake was abolished by 0.5, 1.0, and 2.0mg/kg amphetamine, and no tolerance was observed to this effect. Longer-term hypophagia was produced by 1.0 and 2.0 but not by 0.5mg/kg. Tolerance to longer-term hypophagia was seen when 1.0mg/kg alone was used as the day 3 treatment, but not when 1.0 and 2.0mg/kg were alternated across tests as the day 3 treatment. Short- and longer-term hypophagia were dissociated by threshold doses for elicitation and by differential tolerance. Occasional receipt of a higher amphetamine dose may sometimes increase the longer-term hypophagia produced by a lower dose.

Chronic amphetamine treatment reduces NGF and BDNF in the rat brain

Amphetamines (methamphetamine and d-amphetamine) are dopaminergic and noradrenergic agonists and are highly addictive drugs with neurotoxic effect on the brain. In human subjects, it has also been observed that amphetamine causes psychosis resembling positive symptoms of schizophrenia. Neurotrophins are molecules involved in neuronal survival and plasticity and protect neurons against (BDNF) are the most abundant neurotrophins in the central nervous system (CNS) and are important survival factors for cholinergic and dopaminergic neurons. Interestingly, it has been proposed that deficits in the production or utilization of neurotrophins participate in the pathogenesis of schizophrenia. In this study in order to investigate the mechanism of amphetamine-induced neurotoxicity and further elucidate the role of neurotrophins in the pathogenesis of schizophrenia we administered intraperitoneally d-amphetamine for 8 days to rats and measured the levels of neurotrophins NGF and BDNF in selected brain regions by ELISA. Amphetamine reduced NGF levels in the hippocampus, occipital cortex and hypothalamus and of BDNF in the occipital cortex and hypothalamus. Thus the present data indicate that chronic amphetamine can reduce the levels of NGF and BDNF in selected brain regions. This reduction may account for some of the effects of amphetamine in the CNS neurons and provides evidences for the role of neurotrophins in schizophrenia.

Hypothalamic neuropeptide Y (NPY) and the attenuation of hyperphagia in streptozotocin diabetic rats treated with dopamine D1/D2 agonists

1. Dopamine is an appetite suppressant, while neuropeptide Y (NPY), an appetite stimulant in the brain, is reported to be involved in anorectic action induced by a combined administration of D1/D2 agonists in normal rats. In diabetic rats, however, these factors have not been studied. 2. Rats (including normal, diabetic and insulin-treated diabetic rats) were given daily injections of saline or D1/D2 agonists for 6 days. Changes in food intake and hypothalamic NPY content of these rats were assessed and compared. 3. The D1/D2 agonist-induced anorectic responses were altered in diabetic rats compared to normal rats treated similarly. Both the anorectic response on the first day of dosing and the tolerant response on the subsequent days were attenuated. 4. This alteration was independent of the neuroendocrine disturbance on feeding behavior since the basic pattern of food intake during the time course of a 24-h day/night cycle was similar in normal and diabetic rats; the decrease of food intake following drug treatment was only shown at the initial interval of 0-6 h in both groups of rats. 5. However, this alteration coincided with changes in NPY content following D1/D2 coadministration. The replacement of insulin in diabetic rats could normalize both NPY content and D1/D2 agonist-induced anorexia. 6. It is demonstrated that the response of D1/D2 agonist-induced appetite suppression is attenuated in diabetic rats compared to normal rats and that elevated hypothalamic NPY content may contribute to this alteration.