Psychobiotics correspond to a class of probiotics, mainly of the genus Lactobacillus and Bifidobacterium, capable of producing neuroactive substances, such as γ-aminobutyric acid (GABA) and serotonin, which exert effects on the brain-gut axis. Evidence suggests that psychobiotics can have a beneficial effect on mood, anxiety and cognition. The present study evaluated the effects of chronic administration of two new strains of Lactobacillus plantarum, L. plantarum 286 (Lp 286) and L. plantarum 81 (Lp 81) isolated from the fermentation of cocoa (Theobroma cacao L.) and cupuaçu (Theobroma grandiflorum), respectively, on cognitive, anxiety-and depressive-like behaviors in male Swiss mice. Different groups of animals were administered (oral gavage) solutions of vehicle (0.85% saline plus 15% skim milk), Lp 286 (10 9 /0.1 ml CFU) or Lp 81 (10 9 /0.1 ml CFU) for 30 days, and animals were tested for general locomotor activity, depressive-like behavior in the forced swim test, and learning/memory and anxiety-like behavior in the plus-maze discriminative avoidance task. Treatment with the strains Lp 286 and Lp 81 did not interfere with locomotor activity or learning and memory. The Lp 286 strain exerted anti-depressant-and anxiolytic-like effects under our experimental conditions. Our findings add to the current body of evidence suggesting that probiotics from the genus Lactobacillus may exert psychobiotic potential and introduce a new strain, Lp 286, as a potential candidate in the prevention or as therapeutic adjuvant in the treatment of mental disorders.

Ayahuasca is a hallucinogenic beverage produced from the decoction of Banisteriopsis caapi (Bc) and Psychotria viridis (Pv), β-carboline- and N,N-dimethyltryptamine(DMT)-containing plants, respectively. Accumulating evidence suggests that ayahuasca may have therapeutic effects on ethanol abuse. It is not known, however, whether its effects are dependent on the presence of DMT or if non-DMT-containing components would have therapeutic effects. The aim of the present study was to investigate the rewarding properties of ayahuasca (30, 100, and 300 mg/kg, orally), Bc (132, 440, and 1320 mg/kg, orally) and Pv (3.75, 12.5 and 37.5 mg/kg, i.p.) extracts and their effects on ethanol (1.8 g/kg, i.p.) reward using the conditioned place preference (CPP) paradigm in male mice. Animals were conditioned with ayahuasca, Bc or Pv extracts during 8 sessions. An intermediate, but not a high, dose of ayahuasca induced CPP in mice. Bc and Pv did not induce CPP. Subsequently, the effects of those extracts were tested on the development of ethanol-induced CPP. Ayahuasca, Bc or Pv were administered before ethanol injections during conditioning sessions. While Bc and Pv exerted no effects on ethanol-induced CPP, pretreatment with ayahuasca blocked the development of CPP to ethanol. Finally, the effects of a post-ethanol-conditioning treatment with ayahuasca, Bc or Pv on the expression of ethanol-induced CPP were tested. Animals were conditioned with ethanol, and subsequently treated with either ayahuasca, Bc or Pv in the CPP environment previously associated with saline or ethanol for 6 days. Animals were then reexposed to ethanol and ethanol-induced CPP was quantified on the following day. Treatment with all compounds in the ethanol-paired environment blocked the expression of ethanol-induced CPP. Administration of an intermediate, but not a high, dose of ayahuasca and Bc, as well as Pv administration, in the saline-paired compartment blocked the expression of ethanol-induced CPP. The present study sheds light into the components underlying the therapeutic effects of ayahuasca on ethanol abuse, indicating that ayahuasca and its plant components can decrease ethanol reward at doses that do not exert abuse liability. Importantly, the treatment environment seems to influence the therapeutic effects of ayahuasca and Bc, providing important insights into clinical practice.

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Ibogaine is a psychedelic extracted from the plant Tabernanthe iboga Baill. (Apocynaceae), natural from Africa, and has been proposed as a potential treatment for substance use disorders. In animal models, ibogaine reduces ethanol self-administration. However, no study to date has investigated the effects of ibogaine on ethanol-induced conditioned place preference (CPP). The present study aimed to investigate the effects of repeated treatment with ibogaine on the reinstatement of CPP to ethanol in male mice. The rewarding effects of ethanol (1.8 g/kg, i. p.) or ibogaine (10 or 30 mg/kg, p. o.) were investigated using the CPP model. Furthermore, we evaluated the effects of repeated treatment with ibogaine (10 or 30 mg/kg, p. o.) on the reinstatement of ethanol-induced CPP. Reinstatement was evaluated under two conditions: 1) during a priming injection re-exposure test in which animals received a priming injection of ethanol and had free access to the CPP apparatus; 2) during a drug-free test conducted 24 h after a context-paired re-exposure, in which subjects received an injection of ethanol and were confined to the compartment previously conditioned to ethanol. Our results show that ethanol, but not ibogaine, induced CPP in mice. Treatment with ibogaine after conditioning with ethanol blocked the reinstatement of ethanol-induced CPP, both during a drug priming reinstatement test and during a drug-free test conducted after re-exposure to ethanol in the ethanol-paired compartment. Our findings add to the literature suggesting that psychedelics, in particular ibogaine, may have therapeutic properties for the treatment of alcohol use disorder at doses that do not have rewarding effects per se.

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Introduction: The endocannabinoid system has been implicated in the neurobiology of opioid use disorder. While the CB1 receptor antagonist rimonabant has been shown to block some of the behavioral effects of opioids, studies suggest that the treatment environment (i.e., receiving treatment in the drug-associated environment, and/or novelty) can influence its effects. In the present study, we investigated the role of the treatment environment in the effects of rimonabant on the expression of morphine-induced behavioral sensitization.Methods: Adult female Swiss mice were submitted to a behavioral sensitization protocol, during which they received morphine (20 mg/kg, i.p.) in the open-field apparatus, and were subsequently treated with vehicle or rimonabant (1 or 10 mg/kg, i.p.) either in the open-field, in the home-cage or in an activity box (novel environment). The expression of conditioned locomotion (increased locomotor activity in the open-field apparatus in the absence of morphine) and of morphine-induced behavioral sensitization (increased locomotor activity in animals sensitized to morphine) was evaluated during asubsequent saline and morphine challenge, respectively.Results: Animals treated with morphine expressed behavioral sensitization, showing a significant increase in locomotor activity over time. Animals sensitized to morphine and treated with vehicle in the home-cage expressed conditioned locomotion, an effect that was blocked by home-cage treatment with rimonabant. During a saline challenge, only animals sensitized to morphine and treated with saline in the home-cage expressed morphine-induced conditioned locomotion. All morphine-treated animals that received saline during the treatment phase (control groups) expressed behavioral sensitization during the morphine challenge. Treatment with rimonabant in the open-field and in the activity box, but not in the home-cage, blocked the expression of morphine-induced behavioral sensitization.Discussion: Our findings suggest that CB1 receptor antagonism can modulate conditioned responses to morphine even when administered in the home-cage. However, exposure to the drug-associated environment or to a novel environment is necessary for the expression of rimonabant’s effects on morphine-induced behavioral sensitization during a morphine challenge.

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