ABSTRACT
The use of the hallucinogenic brew ayahuasca, obtained from infusing the shredded stalk of the malpighiaceous plant Banisteriopsis caapi with the leaves of other plants such as Psychotria viridis, is growing in urban centers of Europe, South and North America in the last several decades. Despite this diffusion, little is known about its effects on emotional states. The present study investigated the effects of ayahuasca on psychometric measures of anxiety, panic-like and hopelessness in members of the Santo Daime, an ayahuasca-using religion. Standard questionnaires were used to evaluate state-anxiety (STAI-state), trait-anxiety (STAI-trait), panic-like (ASI-R) and hopelessness (BHS) in participants that ingested ayahuasca for at least 10 consecutive years. The study was done in the Santo Daime church, where the questionnaires were administered 1h after the ingestion of the brew, in a double-blind, placebo-controlled procedure. While under the acute effects of ayahuasca, participants scored lower on the scales for panic and hopelessness related states. Ayahuasca ingestion did not modify state- or trait-anxiety. The results are discussed in terms of the possible use of ayahuasca in alleviating signs of hopelessness and panic-like related symptoms.
Subject(s)
Anxiety/drug therapy , Banisteriopsis/chemistry , Depressive Disorder/drug therapy , Panic/drug effects , Plant Extracts/pharmacology , Adult , Anxiety/psychology , Beverages , Brazil , Depressive Disorder/psychology , Double-Blind Method , Female , Fruit/chemistry , Harmaline/administration & dosage , Harmaline/chemistry , Harmaline/pharmacology , Harmine/administration & dosage , Harmine/analogs & derivatives , Harmine/chemistry , Harmine/pharmacology , Humans , Male , Middle Aged , Molecular Structure , N,N-Dimethyltryptamine/administration & dosage , N,N-Dimethyltryptamine/chemistry , N,N-Dimethyltryptamine/pharmacology , Plant Extracts/administration & dosage , Plant Extracts/chemistry , Plant Leaves/chemistry , Psychometrics/methods , Religion , Surveys and Questionnaires , Treatment OutcomeABSTRACT
The effect of the non-selective 5-HT2C receptor agonist trifluoromethyl-phenylpiperazine (TFMPP, 0.75, 1.5 and 3.0 microg) and the preferential 5-HT2C agonist 6-chloro-2(1-piperazinyl)pyrazine (MK-212, 0.1, 0.3 and 1.0 microg) microinjected into the ventral or dorsal hippocampus was investigated in anxiety measures of rats exposed to the elevated plus-maze test. Ventral hippocampal (VH) microinjections of the 0.75 or 1.5 microg doses of TFMPP reduced open-arm exploration without affecting the number of closed-arm entries, indicating a selective anxiogenic profile. The highest dose (3.0 microg) reduced open- and closed-arm entries, suggesting interference in locomotor activity. The 0.1 microg dose of MK-212 also caused a selective anxiogenic effect when microinjected into the ventral hippocampus, without disturbing locomotor activity. Microinjections of the two higher doses of MK-212 (0.3 or 1.0 microg) into the ventral hippocampus led to a decrease of exploration in both arms of the maze. In contrast to the anxiogenic effect observed in the VH, neither TFMPP nor MK-212 significantly changed anxiety measures when microinjected into the dorsal hippocampus. These results suggest that activation of 5-HT2C postsynaptic receptors located in the ventral, but not in the dorsal, hippocampus play an important role in anxiety triggered by the elevated plus-maze test.
Subject(s)
Arousal/drug effects , Fear/drug effects , Hippocampus/drug effects , Maze Learning/drug effects , Piperazines/pharmacology , Pyrazines/pharmacology , Serotonin 5-HT2 Receptor Agonists , Serotonin Receptor Agonists/pharmacology , Animals , Brain Mapping , Dose-Response Relationship, Drug , Male , Microinjections , Rats , Rats, WistarABSTRACT
Ascending 5-HT projections from the median raphe nucleus (MRN), probably to the hippocampus, are implicated in the acquisition of contextual fear (background stimuli), as assessed by freezing behavior. Foreground cues like light, used as a conditioned stimulus (CS) in classical fear conditioning, also cause freezing through thalamic transmission to the amygdala. As the MRN projects to the hippocampus and amygdala, the role of this raphe nucleus in fear conditioning to explicit cues remains to be explained. Here we analyzed the behavior of rats with MRN electrolytic lesions in a contextual conditioning situation and in a fear-potentiated startle procedure. The animals received MRN electrolytic lesions either before or on the day after two consecutive training sessions in which they were submitted to 10 conditioning trials, each in an experimental chamber (same context) where they received foot-shocks (0.6 mA, 1 sec) paired to a 4-sec light CS. Seven to ten days later, the animals were submitted to testing sessions for assessing conditioned fear when they were placed for five shocks, and the duration of contextual freezing was recorded. The animals were then submitted to a fear-potentiated startle in response to a 4-sec light-CS, followed by white noise (100 dB, 50 ms). Control rats (sham) tested in the same context showed more freezing than did rats with pre- or post-training MRN lesions. Startle was clearly potentiated in the presence of light-CS in the sham-lesioned animals. Whereas pre-training lesions reduced both freezing and fear-potentiated startle, the post-training lesions reduced only freezing to context, without changing the fear-potentiated startle. In a second experiment, neurotoxic lesions of the MRN with local injections of N-methyl-D-aspartate or the activation of 5-HT1A somatodendritic auto-receptors of the MRN by microinjections of the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) before the training sessions also reduced the amount of freezing and the fear-potentiated startle. Freezing is a prominent response of contextual fear conditioning, but does not seem to be crucial for the enhancement of the startle reflex by explicit aversive cues. As fear-potentiated startle may be produced in post-training lesioned rats that are unable to freeze to fear contextual stimuli, dissociable systems seem to be recruited in each condition. Thus, contextual fear and fear-potentiated startle are conveyed by distinct 5-HT-mediated circuits of the MRN.
Subject(s)
Conditioning, Classical/physiology , Fear/physiology , Raphe Nuclei/physiology , Serotonin/physiology , 8-Hydroxy-2-(di-n-propylamino)tetralin/pharmacology , Animals , Behavior, Animal , Excitatory Amino Acid Agonists/toxicity , Male , N-Methylaspartate/toxicity , Rats , Rats, Wistar , Receptors, Serotonin/physiology , Serotonin Receptor Agonists/pharmacologyABSTRACT
1. This paper reports an experiment examining the influence of context on latent inhibition using conditioned freezing behavior as an index. 2. Two groups of 8 Wistar rats (290-320 g) were placed in one chamber (Context 2) and either exposed 7 times or not to a sound stimulus (68 dB, 90 s). Two additional groups of 8 rats received the same stimulation in a different environment (Context 1). Next, each rat was required to form a sound-shock (0.2 mA, 1.5 s) association (20 trials) in Context 2. Freezing behavior was measured both during sound (CS) presentation and during an equal period of time immediately preceding the CS. 3. When the test environment was familiar, the conditioning of fear was greater in the non-preexposed than in the CS-preexposed group. Acquisition of conditioned freezing was intermediate when the test environment was unfamiliar, irrespective of CS preexposure. 4. These results further support the context specificity of latent inhibition. In addition, they suggest that novelty interferes with sound-shock associations
