G protein-coupled receptors (GPCRs) constitute the largest family of drug targets, acting through heterotrimeric G proteins. Agonist bound GPCRs promote GDP release from G proteins allowing their activation upon GTP binding. Here, we analyze this process with innovative tools that detect the main states of native Gi proteins: the GDP-bound, the open nucleotide-free and the active GTP-bound states. We show that receptor activation increases the amount of open-state Gi proteins, consistent with GDP release from inactive Gi proteins. We also observe that the active receptor can release GTP from the active Gi protein, to return to an inactive open state. Consistently, receptor activation also promotes the formation of the Gαβγ complex from the GTP-bound state in cells, in agreement with the formation of the receptor-G protein ternary complex. These data suggest that the amount of active GTP-bound form produced upon GPCR activation can be controlled by the receptor-induced GTP release. This control of G protein state equilibrium that depends on the receptor subtype may affect coupling efficacy. These data reveal receptor-dependent G-protein state equilibria and identify GTP release as an additional, context-dependent control point that can shape apparent coupling efficacy.

Adolescence is a developmentally sensitive period during which individuals begin experimenting with drugs of abuse. This window coincides with maturation of brain structures critical to reward and decision-making, including the prefrontal cortex, as well as peripheral physiological systems such as the gut microbiome - making it a period of heightened vulnerability to the long-lasting effects of drug exposure. Work from our lab has shown that manipulations to the gut microbiome influence drug reward, reinforcement, and drug seeking after abstinence. Critically, some of these effects are age-dependent with adolescents demonstrating greater sensitivity to the effects of microbiome disturbance on drug reward. Behavioral changes induced by microbiome disruption occur in parallel with molecular changes in reward-related brain regions like the medial prefrontal cortex. However, whether adolescent microbiome disruption produces alterations in opioid seeking and molecular changes in brain reward regions that persist into early adulthood has not been investigated.

Sickle cell disease (SCD) is characterized by recurrent, debilitating pain. Opioid analgesics are routinely used in its management, but limited efficacy and pervasive side effects prompt many patients with SCD to seek alternatives, including cannabis. Prior work has shown that 2 major cannabis constituents, Δ[9]-tetrahydrocannabinol (Δ[9]-THC) and cannabidiol (CBD), exert antinociceptive effects in HbSS-BERK mice, a model of SCD. The present study investigated the pharmacological interaction between these 2 agents and characterized the effects associated with repeated coadministration. Fixed-ratio isobolographic analyses demonstrated that Δ[9]-THC and CBD produced dose-dependent antinociception following acute coadministration. Fixed-ratio isobolographic analyses showed that the experimentally determined median effective dose of the mixture was lower than the theoretical additive dose, but the difference was not statistically significant, supporting an additive antinociceptive interaction. Repeated coadministration maintained antinociceptive efficacy over 14 days and reduced SCD-evoked anxiety-like behavior in one cohort but did not improve recognition-memory deficits. Liquid chromatography-tandem mass spectrometry analyses revealed that repeated coadministration increased plasma CBD concentrations, produced a modest increase in Δ[9]-THC exposure, and markedly elevated circulating levels of the endocannabinoid 2-arachidonoyl-sn-glycerol. Molecular analyses of spinal cord tissue showed that HbSS-BERK mice exhibited increased oxidative stress (malondialdehyde, MDA) and proinflammatory signaling (interleukin [IL]-1β mRNA), with no change in anti-inflammatory signaling (IL-10 mRNA). Following 14 days of treatment, CBD reduced MDA and IL-1β transcription, whereas Δ[9]-THC reduced MDA and increased IL-10. Notably, the combination treatment simultaneously reduced oxidative stress, suppressed IL-1β, and enhanced IL-10. Together, these findings demonstrate an additive antinociceptive interaction between Δ[9]-THC and CBD and sustained efficacy during repeated administration in SCD mice. SIGNIFICANCE STATEMENT: Chronic pain in sickle cell disease remains difficult to treat, and many patients use cannabis despite limited understanding of how its constituents interact to produce analgesia. This study demonstrates that the 2 major phytocannabinoids in cannabis, Δ[9]-tetrahydrocannabinol and cannabidiol, produce additive antinociceptive effects in a humanized mouse model of sickle cell disease, and their combined efficacy is maintained during repeated administration without detectable tolerance.

Most often sold in the United States as a dietary supplement, nootropic, or research chemical, tianeptine has become better known by the troubling nickname "gas station heroin." At high doses, it can produce opioid-like effects and lead to dependence, severe withdrawal, poisoning, and even death. This article traces how tianeptine entered the U.S. market and how it is promoted, resulting in the alarming present-day use trends. Attention is given to a large problem: tianeptine is typically excluded from conventional, immunoassay-based routine drug panels, necessitating targeted chromatographic-mass spectrometric toxicology panels for definitive identification. As a result, its use may go unnoticed in treatment programs, workplaces, and criminal justice settings. Although specialized toxicology tests can identify the drug, they are not widely used and are often costly. General substance-use screening instruments cannot establish tianeptine exposure alone; however, when used along with structured interviews, they can help identify broader substance-use risk by uncovering patterns of misuse, including the use of multiple substances and over-the-counter products. Asking direct questions and combining screening methods may help professionals recognize tianeptine use earlier so intervention can begin.

Cannabis and cannabinoid products are increasingly used by patients with cancer for symptom management and supportive care. Although cannabis is widely used to alleviate cancer- and treatment-related symptoms, many patients also believe that it possesses direct anticancer activity. This review provides a comprehensive pharmacologic and clinical assessment of cannabinoids in oncology, integrating the endocannabinoid system, cannabinoid receptor signaling, pharmacokinetics, therapeutic applications, adverse effects, drug-drug interactions, and emerging antitumor research. The strongest clinical evidence supports selected cannabinoid preparations for refractory chemotherapy-induced nausea and vomiting, whereas evidence for cancer-related pain, appetite stimulation, sleep disturbance, anxiety, and opioid-sparing effects remains limited or inconsistent. Δ[9]-tetrahydrocannabinol (THC) and cannabidiol (CBD) differ substantially in receptor pharmacology, psychoactive effects, metabolism, and toxicity, with important implications for product selection, dosing, and interactions with anticancer and supportive-care medications. Preclinical studies demonstrate antiproliferative, proapoptotic, antiangiogenic, and immunomodulatory effects across multiple tumor models; however, cannabinoid signaling is highly context dependent and may also promote tumor progression in selected settings. Human evidence for direct anticancer activity remains sparse, consisting predominantly of small early-phase studies and observational data, with no established improvement in tumor response, progression-free survival, or overall survival. Particular caution is warranted regarding neuropsychiatric and cardiovascular toxicity, pharmacokinetic drug interactions, and the potential influence of cannabis on immune checkpoint inhibitor outcomes. Overall, cannabinoids have defined but limited roles in supportive oncology, while their direct antitumor potential remains investigational. Future studies should prioritize standardized formulations, pharmacologically informed dosing, rigorous randomized designs, clinically meaningful endpoints, and biomarker-based approaches to define therapeutic benefit and risk.

Activation of heterotrimeric G proteins by G-protein-coupled receptors (GPCRs) requires large-scale opening of the Gα α-helical domain (AHD) to expose the nucleotide-binding site and facilitate GDP-GTP exchange. Although orthosteric ligands are known to modulate GPCR conformation, how these effects propagate to the bound G protein remains unclear. Using single-molecule Förster resonance energy transfer imaging, we monitored AHD motions in Gi proteins coupled to the μ-opioid receptor across different ligand- and nucleotide-bound states. We find that receptor ligands differentially modulate these dynamics from a binding site over 70 Å away, with higher-efficacy agonists accelerating transitions to an open, low-nucleotide-affinity conformation. These data also capture transient AHD intermediates during nucleotide exchange and suggest that allosteric control over the G protein conformational states provides an additional mechanism for encoding opioid efficacy and signaling outcomes.