Behavioral characterization of ayahuasca treatment on Wistar rats in the open field test

Abstract Ayahuasca (AYA) is a psychedelic beverage with therapeutic potential for many mood and anxiety disorders. Although there are some preclinical studies, no published reports have tested the behavioral effects of AYA gavage in animal models. This investigation aimed to characterize the behavior of Wistar rats after acute ingestion of AYA for 40 min in the open field test (OFT). The sample consisted of three experimental groups treated with different dosages of AYA (125, 250, or 500 mg kg-1) and a control group. Each group consisted of 10 participants. After gavage, the number of crossings of the OFT grid lines, latency to enter the central area of the device, grooming frequency, and time spent in the central perimeter of the device were immediately evaluated. Analyses were based on one-way ANOVA and a linear-regression mixture model for longitudinal data. AYA intake did not interfere with habituation. The 500 mg kg-1 group showed a decrease in the time spent in the center of the device and in the number of crossings compared to the control group in the last 10 min. These results suggest that gavage with AYA did not interfere with the results, and the behavioral effects were perceived only between 30 and 40 min after gavage. Taken together, the results indicate that three aspects should be considered in OFT studies of AYA acute effects: the moment when the observation starts, the observation period, and the AYA dosage.

Ayahuasca prevents oxidative stress in a rat model of depression elicited by unpredictable chronic mild stress

ABSTRACT Background: Depression is a highly disabling common mental disorder and, due to its multifactorial nature, the development of effective therapies is challenging and of great relevance. Ayahuasca (AYA), an entheogenic traditional beverage, has emerged as an alternative for antidepressant treatment, however, AYA preclinical and clinical trials are still incipient. Objectives: This investigation aimed to evaluate some behavioral and biochemical effects of AYA subchronic administration in rats submitted to a model of depression elicited by unpredictable chronic mild stress (UCMS). Methods: 500 mg/kg of AYA was administered in adult male rats once a day for 15 days before submitting the animals to UCMS. Anhedonia-like and locomotion behavior, lipid peroxidation, antioxidant enzyme activities, and sulfhydryl/nitrite content were evaluated. Results: AYA intake failed to prevent anhedonia-like behavior. Locomotion was not altered by AYA consumption or by the experimental condition. UCMS increased TBARS and nitrites levels, decreased the levels of catalase in the cerebral cortex and of Sulfhydryl in the hippocampus. AYA treatment counteracted these biochemical alterations but did not display any alterations in non-stressed rats. Conclusions: Taken together, results indicate an adaptogenic antioxidant molecular mechanism of AYA in relation to depression induced by stress.

Modulation of adenosine signaling prevents scopolamine-induced cognitive impairment in zebrafish.

Adenosine, a purine ribonucleoside, exhibits neuromodulatory and neuroprotective effects in the brain and is involved in memory formation and cognitive function. Adenosine signaling is mediated by adenosine receptors (A1, A2A, A2B, and A3); in turn, nucleotide and nucleoside-metabolizing enzymes and adenosine transporters regulate its levels. Scopolamine, a muscarinic cholinergic receptor antagonist, has profound amnesic effects in a variety of learning paradigms and has been used to induce cognitive deficits in animal models. This study investigated the effects of acute exposure to caffeine (a non-selective antagonist of adenosine receptors A1 and A2A), ZM 241385 (adenosine receptor A2A antagonist), DPCPX (adenosine receptor A1 antagonist), dipyridamole (inhibitor of nucleoside transporters) and EHNA (inhibitor of adenosine deaminase) in a model of pharmacological cognitive impairment induced by scopolamine in adult zebrafish. Caffeine, ZM 241385, DPCPX, dipyridamole, and EHNA were acutely administered independently via i.p. in zebrafish, followed by exposure to scopolamine dissolved in tank water (200µM). These compounds prevented the scopolamine-induced amnesia without impacting locomotor activity or social interaction. Together, these data support the hypothesis that adenosine signaling may modulate memory processing, suggesting that these compounds present a potential preventive strategy against cognitive impairment.

Influence of antidepressant drugs on Ecto-nucleotide pyrophosphatase/phosphodiesterases (E-NPPs) from salivary glands of rats.

Xerostomia is commonly caused by antidepressant drugs and ATP can influence the saliva production. Adenosine is the product of extracellular hydrolysis of adenine nucleotides in submandibular gland cells, which occurs by the action of ectonucleotidases. In this study, we have evaluated the effect of three different antidepressants in ecto-nucleotide pyrophosphatase/phosphodiesterase (E-NPP1-3) activities in cultured cells from salivary glands. Rats received imipramine (10mg/ml), fluoxetine (20mg/ml) or moclobemide (30mg/ml) by oral gavage. The drugs were administered once a day for 14 days. Our results have shown that the hydrolysis of p-nitrophenyl-5'-thymidine monophosphate increased in all treatments. These effects were not consequence of transcriptional control of E-NPP1-3 genes. The results reported here can highlight the importance of ectonucleotidases in the most common side effect caused by antidepressant therapy.

Expression mapping of ectonucleotide pyrophosphatase/phosphodiesterase 1-3 (E-NPP1-3) in different brain structures during rat development.

Ecto-nucleotide pyrophosphatases/phosphodiesterases (E-NPPs) are membrane-bound ecto-enzymes involved in the modulation of purinergic signaling. Important physiological roles related to brain development have been associated to purinergic neurotransmission. NPP1, two splice isoforms of NPP2, and NPP3 have already been identified in adult rat brain. However, there are no studies evaluating the mRNA expression of these NPP members during the brain development. The effort of the present study was to map NPP gene expression pattern in olfactory bulb, hippocampus, cerebral cortex, striatum, and cerebellum at crucial ages for rat development (7, 14, 21, 60, and 150 days old) by a semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) strategy. Our results demonstrated an increase in the relative expression of NPP1 throughout the aging in all structures analyzed, except in hippocampus, where the higher expression has been detected in 14 days old rats. Both NPP2 isoforms have shown a similar pattern of expression among all structures. The relative expression of NPP3 decreased during the aging mainly on cerebellum, hippocampus, and olfactory bulb. Altogether, the different patterns of NPP gene expression during rat brain development reinforce the idea that each enzyme may play a distinct role on modulating the purinergic signaling throughout aging.

Antiepileptic drugs prevent changes induced by pilocarpine model of epilepsy in brain ecto-nucleotidases.

Ecto-nucleotidases, one of the main mechanisms involved in the control of adenosine levels in the synaptic cleft, have shown increased activities after the pilocarpine model of epilepsy. Here we have investigated the effect of the antiepileptic drugs (AEDs) on ecto-nucleotidase activities from hippocampal and cerebral cortical synaptosomes of rats at seven days after the induction of the pilocarpine model. Expression of these enzymes were investigated as well. Our results have demonstrated that phenytoin (50 mg/kg) and carbamazepine (30 mg/kg) were able to prevent the increase in ecto-nucleotidase activities elicited by pilocarpine in brain synaptosomes. However, sodium valproate (at 100 mg/kg) was only able to avoid the increase on ATP and ADP hydrolysis in hippocampal synaptosomes. Increase on ATP hydrolysis in hippocampal synaptosomes was also prevented by sodium valproate at 286 mg/kg, which corresponds to ED50 for pilocarpine model. NTPDase1, NTPDase2, NTPDase3, and ecto-5'-nucleotidase expressions were not affected by pilocarpine in cerebral cortex. However, expressions of NTPDase2, NTPDase3, and ecto-5'-nucleotidase were increased by pilocarpine in hippocampus. Our results have indicated that previous treatment with AEDs was able to prevent the increase in hippocampal ecto-nucleotidases of pilocarpine-treated rats. These findings have shown that anticonvulsant drugs can modulate plastic events related to the increase of nucleotidase expression and activities in pilocarpine-treated rats.

Nucleotidase activities in membrane preparations of nervous ganglia and digestive gland of the snail Helix aspersa.

Nucleotide-metabolizing enzymes play an important role in the regulation of nucleotide levels. In the present report, we demonstrated an enzyme activity with different kinetic properties in membrane preparations of the nervous ganglia and digestive gland from Helix aspersa. ATPase and ADPase activities were dependent on Ca2+ and Mg2+ with pH optima approximately 7.2 and between 6.0 and 8.0 in digestive gland and nervous ganglia, respectively. The enzyme activities present in membrane preparations of these tissues preferentially hydrolyzed triphosphate nucleotides. In nervous ganglia, the enzyme was insensitive to the classical ATPases inhibitors. In contrast, in digestive gland, N-ethylmaleimide (NEM) produced 45% inhibition of Ca(2+)-ATP hydrolysis. Sodium azide, at 100 microM and 20 mM, inhibited Mg(2+)-ATP hydrolysis by 36% and 55% in digestive gland, respectively. The presence of nucleotide-metabolizing enzymes in these tissues may be important for the modulation of nucleotide and nucleoside levels, controlling their actions on specific purinoceptors in these species.

Effects of starvation on haemolymphatic glucose levels, glycogen contents and nucleotidase activities in different tissues of Helix aspersa (Müller, 1774) (Mollusca, Gastropoda).

In the present study, the glucose concentration in the haemolymph and glycogen levels were determined in the various body parts of the Helix aspersa snail after feeding lettuce ad libitum and after various periods of starvation. To characterize the effect of starvation on nucleotidase activity, enzyme assays were performed on membranes of the nervous ganglia and digestive gland. Results demonstrated the maintenance of the haemolymph glucose concentration for up to 30 days of starvation, probably due to the consumption of glycogen from the mantle. In the nervous ganglia, depletion of glycogen occurs progressively during the different periods of starvation. No significant changes were observed on ATP and ADP hydrolysis in the membranes of nervous ganglia and no alterations in Ca2+ -ATPase and Mg2+ -ATPase occurred in the membranes of the digestive gland of H. aspersa during the different periods of starvation. Although there were no changes in the enzyme activities during starvation, they could be modulated by effectors in situ with concomitant changes in products/reactants during starvation.

Different sensitivity of Ca(2+)-ATPase and cholinesterase to pure and commercial pesticides in nervous ganglia of Phyllocaulis soleiformis (Mollusca).

We measured the effects in vitro of pure and commercial pesticides on Ca(2+)-activated ATPase and cholinesterase (ChE) activities in the nervous system of the slug Phyllocaulis soleiformis. The pesticides used in this study included carbamate and organophosphates, which acts as reversible and irreversible anticholinesterases, respectively. Both enzymes were insensitive to pure carbofuran (1 mM), glyphosate (1 mM) and malathion (120 microM). However, the carbamate carbofuran, in the commercial formulation Furandan 350S, inhibited ATPase and ChE activities. The organophosphate glyphosate used in the commercial preparation of Gliz 480CS inhibited ATPase activity and increased cholinesterase activity. These effects are likely due to the action of adjuvant substances of the chemical formulation. The commercial formulation (Malatol 500CE) did not alter enzymes activities. Our results suggest that cholinesterase present in the slug nervous tissue has a different behavior to those identified in vertebrate nervous tissue, since it was insensitive to pure compounds, known as anticholinesterases in vertebrates. Considering the insensitivity of the Ca(2+)-activated ATPase, we suggested that the purinergic neurotransmission and other roles of ATP might not be affected by the pure pesticides tested.