Role of kappa-opioid receptors in stress and anxiety-related behavior

Pyrrolo- and pyridomorphinans: non-selective opioid antagonists and delta opioid agonists/mu opioid partial agonists

Opioid ligands have found use in a number of therapeutic areas, including for the treatment of pain and opiate addiction (using agonists) and alcohol addiction (using antagonists such as naltrexone and nalmefene). The reaction of imines, derived from the opioid ligands oxymorphone and naltrexone, with Michael acceptors leads to pyridomorphinans with structures similar to known pyrrolo- and indolomorphinans. One of the synthesized compounds, 5e, derived from oxymorphone had substantial agonist activity at delta opioid receptors but not at mu and/or kappa opioid receptors and in that sense profiled as a selective delta opioid receptor agonist. The pyridomorphinans derived from naltrexone and naloxone were all found to be non-selective potent antagonists and as such could have utility as treatments for alcohol abuse.

Antagonists of the kappa opioid receptor

The research community has increasingly focused on the development of OPRK antagonists as pharmacotherapies for the treatment of depression, anxiety, addictive disorders and other psychiatric conditions produced or exacerbated by stress. Short-acting OPRK antagonists have been recently developed as a potential improvement over long-acting prototypic ligands including nor-BNI and JDTic. Remarkably the short-acting LY2456302 is undergoing phase II clinical trials for the augmentation of the antidepressant therapy in treatment-resistant depression. This Letter reviews relevant chemical and pharmacological advances in the identification and development of OPRK antagonists.

Salvinorin A analogs and other κ-opioid receptor compounds as treatments for cocaine abuse

Acute activation of kappa-opioid receptors produces anti-addictive effects by regulating dopamine levels in the brain. Unfortunately, classic kappa-opioid agonists have undesired side effects such as sedation, aversion, and depression, which restrict their clinical use. Salvinorin A (Sal A), a novel kappa-opioid receptor agonist extracted from the plant Salvia divinorum, has been identified as a potential therapy for drug abuse and addiction. Here, we review the preclinical effects of Sal A in comparison with traditional kappa-opioid agonists and several new analogs. Sal A retains the anti-addictive properties of traditional kappa-opioid receptor agonists with several improvements including reduced side effects. However, the rapid metabolism of Sal A makes it undesirable for clinical development. In an effort to improve the pharmacokinetics and tolerability of this compound, kappa-opioid receptor agonists based on the structure of Sal A have been synthesized. While work in this field is still in progress, several analogs with improved pharmacokinetic profiles have been shown to have anti-addictive effects. While in its infancy, it is clear that these compounds hold promise for the future development of anti-addictive therapeutics.

The anti-suicidal potential of buprenorphine: a case report

The very strong relationship between suicide, depressive disorders, and substance use disorders is well recognized. Certain pain syndromes are significantly associated with suicide, irrespective of co-occurring medical or psychiatric diagnosis. Chronic pain, depression, substance use disorders, and suicide appear to involve overlapping neural pathways and brain regions that function in the processing of emotional and physical pain, as well as maintaining reward and anti-reward circuitry. In this article, we employ a clinical case to illustrate how various stressors disrupted the balance between pain and opioid-facilitated analgesia. This disruption resulted in excessive use of short-acting opioids to treat pain with ensuing allostatic overload and culmination in chronic suicidal ideation with a suicide attempt. Sublingual buprenorphine was selected to treat the opioid use disorder. We propose that the unique pharmacodynamics of this drug served to stabilize dysregulated neural circuits, neurotransmitters, and neuropeptides, allowing the mitigation of pain, assuaging opioid cravings, easing depression, and resolving suicidal ideation. To our knowledge, this is the first case report to describe the possible anti-suicidal effect of sublingual buprenorphine.