Heroin-based crack induces hyperalgesia through β-arrestin 2 redistribution and phosphorylation of Erk1/2 and JNK in the periaqueductal gray area

Involvement of CXCL12/CXCR4 in CB2 receptor agonist-attenuated morphine tolerance in Walker 256 tumor-bearing rats with cancer pain

While low-dose cannabinoid 2 (CB2) receptor agonists attenuate morphine tolerance in cancer pain models, chemokine ligand 12 (CXCL12)/chemokine receptor 4 (CXCR4) expression induces morphine tolerance. Whether CB2 receptor agonists attenuate morphine tolerance by modulating CXCL12/CXCR4 signaling or whether CXCL12/CXCR4 signaling affects the mu opioid receptor (MOR) in the development of morphine tolerance in cancer pain remains unclear. In this study, we investigated the attenuation of morphine tolerance by a non-analgesic dose of the CB2 receptor agonist AM1241, focusing specifically on the modulation of CXCL12/CXCR4 signaling and its effect on the MOR. Rats received intrathecal Walker 256 tumor cell implantations and were treated with morphine combined with the intrathecal injection of AM1241 or the CB2 receptor antagonists AM630 and AM1241, or a CXCL12-neutralizing antibody, exogenous CXCL12, or the CXCR4 antagonist AMD3100. Our results show that CXCL12 and CXCR4 levels increased significantly in morphine-tolerant rats and were reduced by AM1241 pretreatment, which was reversed by AM630. CXCL12/CXCR4 expression accelerated the development of morphine tolerance and downregulated MOR expression. CXCR4 colocalized with MOR and CB2. Therefore, a non-analgesic dose of AM1241 attenuated morphine tolerance via CXCL12/CXCR4 signaling, whereas CXCL12/CXCR4 signaling participated in the development of morphine tolerance, potentially by modulating MOR expression in Walker 256 tumor-bearing rats.

Brain-derived neurotrophic factor serum levels as a candidate biomarker for withdrawal in crack heroin dependence

BACKGROUND

Crack heroin is a novel opiate derivative with highly addictive properties and unfamiliar health consequences. It causes a variety of brain dysfunctions that are mediated by neurochemical alterations and abnormal neuroplasticity. Brain-derived neurotrophic factor (BDNF) is a widely recognized biological marker implicated in the neuropathology of substance use during substance use disorder and withdrawal. Its involvement can significantly contribute to the severity of withdrawal symptoms. Hence, this study aimed to evaluate BDNF levels in crack heroin users before and after withdrawal.

METHODS

In this cross-sectional study, 148 male participants were recruited and divided into two groups: persons with crack heroin use disorder (n = 74) and the controls (n = 74). The BDNF serum levels were measured in both crack heroin users and control groups upon hospitalization and again after twenty-one days of withdrawal using the enzyme-linked immunosorbent assay.

RESULTS

The results demonstrated that BDNF levels in persons with crack heroin use disorder upon admission were significantly lower than the levels observed upon discharge and in the control group (p < 0.05). Additionally, a significant difference in BDNF levels was found between persons with crack heroin use disorder at admission and discharge (p = 0.038). Furthermore, BDNF levels showed an inverse correlation with the daily dose of substance use (r= -0.420, p = 0.03) and the duration of crack heroin use (r= -0.235, p = 0.001).

CONCLUSIONS

A progressive increment in BDNF levels during early detoxification is associated with the daily amount of substance use and the duration of substance use. Our findings suggest that changes in BDNF serum levels during crack heroin use disorder and withdrawal could serve as potential biomarkers for assessing the intensity of withdrawal symptoms and substance use-related behaviors.

New Horizons: Is Obesity a Disorder of Neurotransmission?

Obesity is a disease of the nervous system. While some will view this statement as provocative, others will take it as obvious. Whatever our side is, the pharmacology tells us that targeting the nervous system works for promoting weight loss. It works, but at what cost? Is the nervous system a safe target for sustainable treatment of obesity? What have we learned-and unlearned-about the central control of energy balance in the last few years? Herein we provide a thought-provoking exploration of obesity as a disorder of neurotransmission. We discuss the state of knowledge on the brain pathways regulating energy homeostasis that are commonly targeted in anti-obesity therapy and explore how medications affecting neurotransmission such as atypical antipsychotics, antidepressants, and antihistamines relate to body weight. Our goal is to provide the endocrine community with a conceptual framework that will help expending our understanding of the pathophysiology of obesity, a disease of the nervous system.

Evaluating oliceridine as a treatment option for moderate to severe acute post-operative pain in adults

INTRODUCTION

Despite the advances in regional anesthesia and non-opioid systemic analgesia, opioids remain the primary rescue analgesic for moderate to severe pain. However, the risks and side effects of opioid medications are well documented. Oliceridine is a novel opioid receptor agonist which is thought to have less risk of adverse events, such as postoperative nausea and vomiting (PONV) and respiratory depression.

AREAS COVERED

In this review, the authors discuss the limitations of the current opioid and non-opioid analgesic options. They also review the pharmacokinetics of oliceridine, its analgesic efficacy, and risk of adverse events; and its added clinical value in managing moderate to severe pain.

EXPERT OPINION

Despite the advances in regional anesthesia and multimodal systemic analgesia, opioid free analgesia is only feasible in selected procedures and patients. Oliceridine is effective in the management of moderate to severe pain and appears to be associated with lower risk of nausea and vomiting. The risk of sedation and respiratory depression associated with oliceridine will require further study. The availability of an opioid agonist with a better side effect profile could potentially change the current paradigm of opioid avoidance in postoperative pain management.

Barbadin Potentiates Long-Term Effects of Lorcaserin on POMC Neurons and Weight Loss

Obesity is a serious global health problem because of its increasing prevalence and comorbidities, but its treatments are limited. The serotonin 2C receptor (5-HT2CR), a G-protein-coupled receptor, activates proopiomelanocortin (POMC) neurons in the arcuate nucleus of hypothalamus (ARH) to reduce appetite and weight gain. However, several 5-HT analogs targeting this receptor, e.g., lorcaserin (Lor), suffer from diminished efficacy to reduce weight after prolonged administration. Here, we show that barbadin (Bar), a novel β-arrestin/β2-adaptin inhibitor, can prevent 5-HT2CR internalization in cells and potentiate long-term effects of Lor to reduce appetite and body weight in male mice. Mechanistically, we demonstrate that Bar co-treatment can effectively maintain the sensitivity of the 5-HT2CR in POMCARH neurons, despite prolonged Lor exposure, thereby allowing these neurons to be activated through opening the transient receptor potential cation (TRPC) channels. Thus, our results prove the concept that inhibition of 5-HT2CR desensitization can be a valid strategy to improve the long-term weight loss effects of Lor or other 5-HT2CR agonists, and also provide an intellectual framework to develop effective long-term management of weight by targeting 5-HT2CR desensitization.SIGNIFICANCE STATEMENT By demonstrating that the combination of barbadin (Bar) with a G-protein-coupled receptor (GPCR) agonist can provide prolonged weight-lowering benefits in a preclinical setting, our work should call for additional efforts to validate Bar as a safe and effective medicine or to use Bar as a lead compound to develop more suitable compounds for obesity treatment. These results prove the concept that inhibition of serotonin 2C receptor (5-HT2CR) desensitization can be a valid strategy to improve the long-term weight loss effects of lorcaserin (Lor) or other 5-HT2CR agonists. Since GPCRs represent a major category as therapeutic targets for various human diseases and desensitization of GPCRs is a common issue, our work may provide a conceptual framework to enhance effects of a broad range of GPCR medicines.