Ibogaine acts at the nicotinic acetylcholine receptor to inhibit catecholamine release

The Bright Side of Psychedelics: Latest Advances and Challenges in Neuropharmacology

The need to identify effective therapies for the treatment of psychiatric disorders is a particularly important issue in modern societies. In addition, difficulties in finding new drugs have led pharmacologists to review and re-evaluate some past molecules, including psychedelics. For several years there has been growing interest among psychotherapists in psilocybin or lysergic acid diethylamide for the treatment of obsessive-compulsive disorder, of depression, or of post-traumatic stress disorder, although results are not always clear and definitive. In fact, the mechanisms of action of psychedelics are not yet fully understood and some molecular aspects have yet to be well defined. Thus, this review aims to summarize the ethnobotanical uses of the best-known psychedelic plants and the pharmacological mechanisms of the main active ingredients they contain. Furthermore, an up-to-date overview of structural and computational studies performed to evaluate the affinity and binding modes to biologically relevant receptors of ibogaine, mescaline, N,N-dimethyltryptamine, psilocin, and lysergic acid diethylamide is presented. Finally, the most recent clinical studies evaluating the efficacy of psychedelic molecules in some psychiatric disorders are discussed and compared with drugs already used in therapy.

Three Naturally-Occurring Psychedelics and Their Significance in the Treatment of Mental Health Disorders

Classical psychedelics represent a family of psychoactive substances with structural similarities to serotonin and affinity for serotonin receptors. A growing number of studies have found that psychedelics can be effective in treating various psychiatric conditions, including post-traumatic stress disorder, major depressive disorder, anxiety, and substance use disorders. Mental health disorders are extremely prevalent in the general population constituting a major problem for the public health. There are a wide variety of interventions for mental health disorders, including pharmacological therapies and psychotherapies, however, treatment resistance still remains a particular challenge in this field, and relapse rates are also quite high. In recent years, psychedelics have become one of the promising new tools for the treatment of mental health disorders. In this review, we will discuss the three classic serotonergic naturally occurring psychedelics, psilocybin, ibogaine, and N, N-dimethyltryptamine, focusing on their pharmacological properties and clinical potential. The purpose of this article is to provide a focused review of the most relevant research into the therapeutic potential of these substances and their possible integration as alternative or adjuvant options to existing pharmacological and psychological therapies.

Ethnopharmacological Applications Targeting Alcohol Abuse: Overview and Outlook

Excessive alcohol consumption is the cause of several diseases and thus is of a major concern for society. Worldwide alcohol consumption has increased by many folds over the past decades. This urgently calls for intervention and relapse counteract measures. Modern pharmacological solutions induce complete alcohol self-restraint and prevent relapse, but they have many side effects. Natural products are most promising as they cause fewer adverse effects. Here we discuss in detail the medicinal plants used in various traditional/folklore medicine systems for targeting alcohol abuse. We also comprehensively describe preclinical and clinical studies done on some of these plants along with the possible mechanisms of action.

Chinese Herbal Medicine for the Treatment of Drug Addiction

This chapter summarizes recent developments in preclinical and clinical research on Chinese herbal medicines and their neurochemical mechanism of action for the treatment of drug addiction. We searched Chinese and English scientific literature and selected several kinds of Chinese herbal medicines that have beneficial effects on drug addiction. Ginseng (Renshen) may be clinically useful for the prevention of opioid abuse and dependence. Rhizoma Corydalis (Yanhusuo) may be used to prevent relapse to chronic drug dependence. Alkaloids of Uncaria rhynchophylla (Gouteng) appear to have positive effects on methamphetamine and ketamine addiction. Both Salvia miltiorrhiza (Danshen) and Radix Pueraiae (Gegen) have beneficial inhibitory effects on alcohol intake. Sinomenine has been shown to have preventive and curative effects on opioid dependence. l-Stepholidine, an alkaloid extract of the Chinese herb Stephania intermedia (Rulan), attenuated the acquisition, maintenance, and reacquisition of morphine-induced conditioned place preference and antagonized the heroin-induced reinstatement of heroin seeking. Traditional Chinese herbal medicines may be used to complement current treatments for drug addiction, including withdrawal and relapse. As the molecular mechanisms of action of traditional Chinese herbal medicines are elucidated, further advances in their use for the treatment of drug addiction are promising.

Exploring Hallucinogen Pharmacology and Psychedelic Medicine with Zebrafish Models

After decades of sociopolitical obstacles, the field of psychiatry is experiencing a revived interest in the use of hallucinogenic agents to treat brain disorders. Along with the use of ketamine for depression, recent pilot studies have highlighted the efficacy of classic serotonergic hallucinogens, such as lysergic acid diethylamide and psilocybin, in treating addiction, post-traumatic stress disorder, and anxiety. However, many basic pharmacological and toxicological questions remain unanswered with regard to these compounds. In this study, we discuss psychedelic medicine as well as the behavioral and toxicological effects of hallucinogenic drugs in zebrafish. We emphasize this aquatic organism as a model ideally suited to assess both the potential toxic and therapeutic effects of major known classes of hallucinogenic compounds. In addition, novel drugs with hallucinogenic properties can be efficiently screened using zebrafish models. Well-designed preclinical studies utilizing zebrafish can contribute to the reemerging treatment paradigm of psychedelic medicine, leading to new avenues of clinical exploration for psychiatric disorders.

Fatalities temporally associated with the ingestion of ibogaine

Ibogaine is a naturally occurring psychoactive plant alkaloid that is used globally in medical and nonmedical settings for opioid detoxification and other substance use indications. All available autopsy, toxicological, and investigative reports were systematically reviewed for the consecutive series of all known fatalities outside of West Central Africa temporally related to the use of ibogaine from 1990 through 2008. Nineteen individuals (15 men, four women between 24 and 54 years old) are known to have died within 1.5-76 h of taking ibogaine. The clinical and postmortem evidence did not suggest a characteristic syndrome of neurotoxicity. Advanced preexisting medical comorbidities, which were mainly cardiovascular, and/or one or more commonly abused substances explained or contributed to the death in 12 of the 14 cases for which adequate postmortem data were available. Other apparent risk factors include seizures associated with withdrawal from alcohol and benzodiazepines and the uninformed use of ethnopharmacological forms of ibogaine.

Traditional medicine in the treatment of drug addiction

AIMS

To evaluate clinical trials and neurochemical mechanisms of the action of traditional herbal remedies and acupuncture for treating drug addiction.

METHODS

We used computerized literature searches in English and Chinese and examined texts written before these computerized databases existed. We used search terms of treatment and neurobiology of herbal medicines, and acupuncture for drug abuse and dependence.

RESULTS

Acupuncture showed evidence for clinical efficacy and relevant neurobiological mechanisms in opiate withdrawal, but it showed poor efficacy for alcohol and nicotine withdrawal or relapse prevention, and no large studies supported its efficacy for cocaine in well-designed clinical trials. Clinical trials were rare for herbal remedies. Radix Puerariae showed the most promising efficacy for alcoholism by acting through daidzin, which inhibits mitocochondrial aldehyde dehydrogenase 2 and leads to disulfiram-like alcohol reactions. Peyote also has some evidence for alcoholism treatment among Native Americans. Ginseng and Kava lack efficacy data in addictions, and Kava can be hepatotoxic. Thunbergia laurifolia can protect against alcoholic liver toxicity. Withania somnifera and Salvia miltiorrhiza have no efficacy data, but can reduce morphine tolerance and alcohol intake, respectively, in animal models.

CONCLUSIONS

Traditional herbal treatments can compliment pharmacotherapies for drug withdrawal and possibly relapse prevention with less expense and perhaps fewer side effects with notable exceptions. Both acupuncture and herbal treatments need testing as adjuncts to reduce doses and durations of standard pharmacotherapies.

Natural products and derivatives affecting neurotransmission relevant to Alzheimer's and Parkinson's disease

The two major neurodegenerative diseases Alzheimer's disease (AD) and Parkinson's disease (PD) are characterised by low levels in the brain of the neurotransmitters acetylcholine (ACh) and dopamine (DA), respectively. Clinical treatment of these two conditions is palliative and relies, in most cases, on improving stimulation at the relevant receptors by either increasing levels of the endogenous neurotransmitter or by the use of substances which have a similar agonist response. Natural products continue to provide useful drugs in their own right but also provide templates for the development of other compounds. The major advances in the treatment of AD have been the use of acetylcholinesterase inhibitors such as galantamine, huperzine A, physostigmine and its derivatives to increase the levels of ACh rather than the use of cholinergic compounds, although compounds with nicotinic properties have attracted some interest. In contrast, the treatment of PD has relied on the elevation of DA levels by use of L-DOPA, its precursor, and by the administration of dopaminergic agonists, especially the ergot alkaloid derivatives. The use of inhibitors of enzymes that cause breakdown of DA is an avenue which is being explored. As well as the major natural products of clinical interest, the paper discusses the chemistry, activity and usage of the constituents of plants used in traditional medicine for the treatment of diseases presenting symptoms similar to those characteristic for Alzheimer's or Parkinson's disease.

Anti-addictive actions of an iboga alkaloid congener: a novel mechanism for a novel treatment

18-Methoxycoronaridine (18-MC), a novel iboga alkaloid congener that decreases drug self-administration in several animal models, may be a potential treatment for multiple forms of drug abuse. In animal models, 18-MC reduced intravenous morphine, cocaine, methamphetamine and nicotine self-administration, oral alcohol and nicotine intake, and attenuated signs of opioid withdrawal, but had no effect on responding for a nondrug reinforcer (water) and produced no apparent toxicity [Brain Res. 719 (1996) 29; NeuroReport 11 (2000) 2013; Pharmacol. Biochem. Behav. 58 (1997) 615; Psychopharmacology (Berl.) 139 (1998) 274; NeuroReport 9 (1998) 1283; Ann. N. Y. Acad. Sci. 914 (2000) 369]. Consistent with a relationship among drug sensitization, mesolimbic dopamine, and drug-seeking behavior, 18-MC also blocked the sensitized dopamine responses to morphine and cocaine in the nucleus accumbens. An extensive series of receptor studies showed that 18-MC was most potent and somewhat selective as an antagonist at alpha3beta4 nicotinic receptors. Low-dose combinations of 18-MC with other drugs known to have this same action (e.g., mecamylamine, dextromethorphan, bupropion) decreased morphine, methamphetamine, and nicotine self-administration in rats at doses that were ineffective if administered alone. Together, the data support the hypothesis that diencephalic pathways having high densities of alpha3beta4 nicotinic receptors modulate mesocorticolimbic pathways more directly involved in drug reinforcement. Antagonists of alpha3beta4 nicotinic receptors may represent a totally novel approach to treating multiple addictive disorders, and 18-MC might be the first of a new class of synthetic agents acting via this novel mechanism and having a broad spectrum of activity.

Characterization of the discriminable stimulus produced by 2-BFI: effects of imidazoline I(2)-site ligands, MAOIs, beta-carbolines, agmatine and ibogaine

1. The molecular nature and functions of the I(2) subtype of imidazoline binding sites are unknown but evidence suggests an association with monoamine oxidase (MAO). Rats can distinguish the selective imidazoline I(2)-site ligand 2-BFI from vehicle in drug discrimination, indicating functional consequences of occupation of these sites. We have used drug discrimination to investigate the nature of the discriminable stimulus, especially in relation to MAO inhibition. 2. Following training to distinguish 2-BFI 7 mg kg(-1) i.p. from saline vehicle in two-lever operant-chambers, male Hooded Lister rats underwent sessions where test substances were given instead and the proportion of lever presses on the 2-BFI-associated lever (substitution) recorded. 3. 2-BFI; its cogeners BU216, BU224, BU226 and LSL60101; the reversible MAO-A inhibitors moclobemide and RO41-1049; the beta-carbolines harmane, norharmane and harmaline which also reversibly inhibit MAO-A, and the anti-addictive substance ibogaine exhibited potent, dose-dependent substitution for 2-BFI. 4. Agmatine, and LSL60125 substituted at one dose only. The reversible MAO-B inhibitors lazabemide and RO16-1649; the sigma(2)-site ligand SKF10,047 and the I(2A)-site ligand, amiloride, failed to substitute. The irreversible inhibitor of MAO, deprenyl, substituted for 2-BFI while clorgyline did not. 5. These results suggest imidazoline I(2) site ligands produce a common discriminable stimulus that appears associated with reversible inhibition of MAO-A rather than MAO-B, possibly through increases in extracellular concentration of one or more monoamines. Ibogaine exhibits a commonality in its subjective effects with those of I(2)-site ligands.

Antagonism of alpha 3 beta 4 nicotinic receptors as a strategy to reduce opioid and stimulant self-administration

The iboga alkaloid ibogaine and the novel iboga alkaloid congener 18-methoxycoronaridine are putative anti-addictive agents. Using patch-clamp methodology, the actions of ibogaine and 18-methoxycoronaridine at various neurotransmitter receptor ion-channel subtypes were determined. Both ibogaine and 18-methoxycoronaridine were antagonists at alpha 3 beta 4 nicotinic receptors and both agents were more potent at this site than at alpha 4 beta 2 nicotinic receptors or at NMDA or 5-HT(3) receptors; 18-methoxycoronaridine was more selective in this regard than ibogaine. In studies of morphine and methamphetamine self-administration, the effects of low dose combinations of 18-methoxycoronaridine with mecamylamine or dextromethorphan and of mecamylamine with dextromethorphan were assessed. Mecamylamine and dextromethorphan have also been shown to be antagonists at alpha 3 beta 4 nicotinic receptors. All three drug combinations decreased both morphine and methamphetamine self-administration at doses that were ineffective if administered alone. The data are consistent with the hypothesis that antagonism at alpha 3 beta 4 receptors is a potential mechanism to modulate drug seeking behavior. 18-Methoxycoronaridine apparently has greater selectivity for this site than other agents and may be the first of a new class of synthetic agents acting via this novel mechanism to produce a broad spectrum of anti-addictive activity.

The development and expression of locomotor sensitization to nicotine in the presence of ibogaine

Ibogaine is a naturally occurring psychoactive alkaloid with claimed efficacy in the treatment of certain drug addictions, including nicotine. It has been reported to be a non-competitive blocker of nicotinic receptors, with a potent inhibitory action on nicotinic acetylcholine receptor-mediated catecholamine release. We have investigated the effect of different doses of ibogaine on the development and expression of sensitization to the locomotor stimulant effect of nicotine in rats, a facilitatory process in which a history of exposure to nicotine results in enhanced locomotor activity when the same dose of nicotine is administered repeatedly. The effects were determined of co-administering ibogaine (0.0, 5.0 or 10 mg/kg i.p.) with nicotine (0.0 or 0.4 mg/kg s.c.) daily for 21 days. Dose-response curves for nicotine (0.04-0.8 mg/kg s.c.) were then determined in groups of 10 rats. There was clear sensitization of the locomotor activity produced by nicotine in photocell activity cages but co-administration of ibogaine with nicotine had no effect on the degree of sensitization. Ibogaine (5-20 mg/kg) itself did not influence locomotor activity and was also without effect on the expression of the sensitized response to 0.4 mg/kg of nicotine (n = 10). Thus, there was no evidence that ibogaine may retard or suppress sensitization to nicotine.

The effects of ibogaine on dopamine and serotonin transport in rat brain synaptosomes

Ibogaine has been shown to affect biogenic amine levels in selected brain regions. Because of the involvement of these neurotransmitters in drug addiction, the effects of ibogaine on biogenic amine transport may contribute to the potential anti-addictive properties of ibogaine in vivo. With rat brain synaptosomes as our experimental system, we measured the effects of ibogaine on the uptake and release of dopamine (DA) and serotonin (5-HT). Ibogaine competitively blocked both DA and 5-HT uptake with IC50 values of 20 microM at 75 nM 3H-DA and 2.6 microM at 10 nM 3H-5-HT. Ibogaine had no effect on K+-induced release of 3H-DA from preloaded synaptosomes, but 20 microM and 50 microM ibogaine inhibited roughly 40% and 60%, respectively, of the K(+)-induced release of 3H-5-HT from preloaded synaptosomes. In the absence of a depolarizing stimulus, ibogaine evoked a small release of 3H-DA but not 3H-5-HT. These relatively low-potency effects of ibogaine on DA and 5-HT uptake in synaptosomes are consistent with the low binding affinity of ibogaine that has been previously reported for DA and 5-HT transporters. Our results show that if ibogaine modulates DA and 5-HT levels in the brain by directly blocking their uptake, then a concentration of ibogaine in the micromolar range is required. Furthermore, if the anti-addictive effects of ibogaine require this concentration, then ibogaine likely exerts these effects through a combination of neurotransmitter pathways, because binding affinities and functional potencies of ibogaine in the micromolar range have been reported for a variety of neuronal receptors and transporters.