Serotonin 2A Receptor (5-HT2AR) Agonists: Psychedelics and Non-Hallucinogenic Analogues as Emerging Antidepressants

Psychedelic 25H-NBOMe attenuates post-sepsis depression in rats

Sepsis-associated encephalopathy, which manifests in severe cognitive and depressive symptoms, is directly linked to neuroinflammation. Our study investigates the efficacy of 25H-NBOMe, a phenethylamine, in alleviating these symptoms, potentially offering an innovative treatment for post-sepsis depression. Wistar rats, weighing between 250-300 g, were subjected to cecal ligation and puncture (CLP) surgery to induce sepsis. Depressive-like behaviors were assessed using the forced swim test (FST) on either day 7 or 14 post-surgery, to establish the presence of depressive symptoms. The impact of 25H-NBOMe treatment was then evaluated, focusing on the head-twitch response (HTR), performance in the FST, and GFAP expression in the prefrontal cortex. Treatment with 25H-NBOMe resulted in significant behavioral changes, demonstrated by decreased immobility and increased swimming times in the FST, along with a rise in the HTR. These outcomes indicate a reduction in depressive-like symptoms post-sepsis and the psychoactive effects of the compound. Furthermore, a notable decrease in GFAP expression in the study highlights the compound's impact on mitigating sepsis-induced astrogliosis. This study demonstrates the effectiveness of 25H-NBOMe, a psychedelic in the phenethylamine class, in treating post-sepsis depression and reducing astrogliosis. However, the psychedelic nature of 25H-NBOMe calls for further investigation into similar compounds with less psychoactive impact, crucial for advancing treatment options for neuropsychiatric symptoms following sepsis.

G protein-specific mechanisms in the serotonin 5-HT2A receptor regulate psychosis-related effects and memory deficits

G protein-coupled receptors (GPCRs) are sophisticated signaling machines able to simultaneously elicit multiple intracellular signaling pathways upon activation. Complete (in)activation of all pathways can be counterproductive for specific therapeutic applications. This is the case for the serotonin 2 A receptor (5-HT2AR), a prominent target for the treatment of schizophrenia. In this study, we elucidate the complex 5-HT2AR coupling signature in response to different signaling probes, and its physiological consequences by combining computational modeling, in vitro and in vivo experiments with human postmortem brain studies. We show how chemical modification of the endogenous agonist serotonin dramatically impacts the G protein coupling profile of the 5-HT2AR and the associated behavioral responses. Importantly, among these responses, we demonstrate that memory deficits are regulated by Gαq protein activation, whereas psychosis-related behavior is modulated through Gαi1 stimulation. These findings emphasize the complexity of GPCR pharmacology and physiology and open the path to designing improved therapeutics for the treatment of stchizophrenia.

Discovery and Structure-Activity Relationships of 2,5-Dimethoxyphenylpiperidines as Selective Serotonin 5-HT2A Receptor Agonists

Classical psychedelics such as psilocybin, lysergic acid diethylamide (LSD), and N,N-dimethyltryptamine (DMT) are showing promising results in clinical trials for a range of psychiatric indications, including depression, anxiety, and substance abuse disorder. These compounds are characterized by broad pharmacological activity profiles, and while the acute mind-altering effects can be ascribed to their shared agonist activity at the serotonin 2A receptor (5-HT2AR), their apparent persistent therapeutic effects are yet to be decidedly linked to activity at this receptor. We report herein the discovery of 2,5-dimethoxyphenylpiperidines as a novel class of selective 5-HT2AR agonists and detail the structure-activity investigations leading to the identification of LPH-5 [analogue (S)-11] as a selective 5-HT2AR agonist with desirable drug-like properties.

Synthesis and bioactivity of psilocybin analogues containing a stable carbon-phosphorus bond

Psilocybin analogues have been synthesized comprising a non-hydrolysable P-C bond to evaluate the biological activity and the selectivity towards 5-HT2AR, 5-HT2BR and the TNAP receptor. No activity was observed towards the phosphatase, however all compounds showed good binding affinity for 5-HT2AR and 5-HT2BR and one compound showed a higher selectivity towards 5-HT2AR than psilocin.

2-Phenylcyclopropylmethylamine (PCPMA) as a privileged scaffold for central nervous system drug design

The use of privileged scaffolds in medicinal chemistry is an effective way to accelerate the drug discovery process, especially at the hit/lead optimization stage. 2-Phenylcyclopropylmethylamine (PCPMA) is a less commonly used chemical scaffold in medicinal chemistry, but many PCPMA-containing compounds exert therapeutic effects for various diseases, in particular central nervous system (CNS) diseases such as depression, schizophrenia, sleep disorder, and Parkinson's disease. The backbone of the PCPMA scaffold enables a unique structure of an amino group linked to a benzene ring through an alkyl linker, making it a useful template for the design of bioactive compounds especially for CNS drug targets including aminergic GPCRs and transporters. This review summarizes the medicinal chemistry studies of PCPMA-containing drugs and drug-like molecules, their mechanisms of action, and biological activities. We conclude that PCPMA is a unique and useful privileged scaffold for CNS drug design.

Unlocking the biosynthesis of psychedelic-inspired indolethylamines

A recent report by Chen et al. describes the discovery of RmNMT, a highly active and promiscuous tryptamine N-methyltransferase from the cane toad, Rhinella marina. N,N-dimethyltryptamine derivatives produced by this enzyme were then evaluated for their potential to serve as next-generation treatments for mental health disorders.

Are "mystical experiences" essential for antidepressant actions of ketamine and the classic psychedelics?

The growing interest in the rapid and sustained antidepressant effects of the dissociative anesthetic ketamine and classic psychedelics, such as psilocybin, is remarkable. However, both ketamine and psychedelics are known to induce acute mystical experiences; ketamine can cause dissociative symptoms such as out-of-body experience, while psychedelics typically bring about hallucinogenic experiences, like a profound sense of unity with the universe or nature. The role of these mystical experiences in enhancing the antidepressant outcomes for patients with depression is currently an area of ongoing investigation and debate. Clinical studies have shown that the dissociative symptoms following the administration of ketamine or (S)-ketamine (esketamine) are not directly linked to their antidepressant properties. In contrast, the antidepressant potential of (R)-ketamine (arketamine), thought to lack dissociative side effects, has yet to be conclusively proven in large-scale clinical trials. Moreover, although the activation of the serotonin 5-HT2A receptor is crucial for the hallucinogenic effects of psychedelics in humans, its precise role in their antidepressant action is still under discussion. This article explores the importance of mystical experiences in enhancing the antidepressant efficacy of both ketamine and classic psychedelics.