Anxiolytic effect of caffeine and caffeine-clonazepam interaction: evaluation by NaCl solution intake

Periodical reactivation under the effect of caffeine attenuates fear memory expression in rats

In the last decade, several studies have shown that fear memories can be attenuated by interfering with reconsolidation. However, most of the pharmacological agents used in preclinical studies cannot be administered to humans. Caffeine is one of the world’s most popular psychoactive drugs and its effects on cognitive and mood states are well documented. Nevertheless, the influence of caffeine administration on fear memory processing is not as clear. We employed contextual fear conditioning in rats and acute caffeine administration under a standard memory reconsolidation protocol or periodical memory reactivation. Additionally, potential rewarding/aversion and anxiety effects induced by caffeine were evaluated by conditioning place preference or open field, respectively. Caffeine administration was able to attenuate weak fear memories in a standard memory reconsolidation protocol; however, periodical memory reactivation under caffeine effect was necessary to attenuate strong and remote memories. Moreover, caffeine promoted conditioned place preference and anxiolytic-like behavior, suggesting that caffeine weakens the initial learning during reactivation through counterconditioning mechanisms. Thus, our study shows that rewarding and anxiolytic effects of caffeine during fear reactivation can change the emotional valence of fear memory. It brings a new promising pharmacological approach based on drugs widely used such as caffeine to treat fear-related disorders.

Effects of acute caffeine on anxiety-related behavior in rats chronically exposed to the drug, with some evidence of possible withdrawal-reversal

For 20days male and female PVG/c hooded rats were provided with caffeinated (approximately 50mg/kg/day) or unadulterated drinking water, and then their anxiety-related behavior was observed in an open field and elevated plus maze. Their choices of a brightness change were also observed in a Y maze to assess any caffeine effects on spatial memory. 24h later, all rats were tested again following an intraperitoneal injection of 50mg/kg acute caffeine, or vehicle. Earlier chronic caffeine decreased ambulation, walking, rearing, center occupancy and increased immobility in the open field thereby suggesting increased anxiety. However, occupancy of the plus-maze open arms and the Y-maze novel arm were increased by caffeine for male rats, but decreased for females probably because of sex differences in control levels of the response rather than to drug effects on anxiety and memory respectively. Following caffeine withdrawal, acute caffeine had the opposite effect to chronic treatment namely, increased open-field ambulation, walking, center occupancy and decreased immobility and defecation for caffeine-naïve rats that were suggestive of decreased anxiety. Similar but more consistent effects (plus decreased emergence latencies from a darkened start box into the open field) also typified the caffeine-experienced rats which in this case may have been accentuated by caffeine withdrawal-reversal. There was no evidence of either chronic or acute caffeine affecting spatial memory measured in the Y maze. There were also examples of lower overall activity and higher anxiety in male rats, than in females, and some sex-dependent caffeine effects.

Modulatory effects of caffeine on oxidative stress and anxiety-like behavior in ovariectomized rats

Menopause is accompanied by enhanced oxidative stress and behavioral changes, effects attenuated by antioxidants. The aim of this study was to evaluate the effects of caffeine on behavior and oxidative stress in an experimental model of menopause. Female rats were divided into the following groups: sham-operated (CON), sham-operated and caffeine-treated (CAF), ovariectomized (OVX), ovariectomized and caffeine-treated (OVX+CAF). Caffeine (6 mg/kg) and vehicle were administered for 21 days (subchronic) and 42 days (chronic), using 2 experimental subsets. Behavioral tests and oxidative stress parameters in the blood, whole brain, and hippocampus were assessed. The subchronic administration of caffeine decreased the lipid peroxidation and improved the antioxidant defense in the blood and brain. The GSH/GGSG ratio in the brain was improved by chronic administration, with reduced activities of antioxidant enzymes and enhanced nitric oxide and malondialdehyde levels. In particular, the lipid peroxidation in the hippocampus decreased in both experiments. The rats became hyperactive after 21 days of treatment, but no effect was observed after chronic administration. In both experimental subsets, caffeine had anxiolytic effects as tested in elevated plus maze. The administration of low doses of caffeine, for a short period of time, may be a new therapeutic approach to modulating the oxidative stress and anxiety in menopause.

Pharmaceutical properties and toxicology of Dioclea grandiflora

CONTEXT

Since the beginning of civilization, herbal medicines have been an important source for human beings to treat their ailments. Despite the large number of synthetic remedies available in the market, the use of plants is seen as a great challenge in the search for new substances endowed with therapeutic properties. One example is Dioclea grandiflora Mart. ex Benth. (Leguminosae) employed in traditional medicine to treat prostate disorders and kidney stones.

OBJECTIVES

This work presents a brief overview of D. grandiflora, including a description of the plant, its chemical composition and pharmacological properties.

METHODS

This review gathers information available in the scientific literature compiled from databases such as Science Direct, PubMed, Dr. Dukes Phytochemical and Ethnobotany, Missouri Botanical Garden and The International Plant Names Index.

RESULTS

The information found in the literature showed that flavonoids are the major constituents of D. grandiflora that account for most of the pharmacological properties so far disclosed. Several studies have revealed that D. grandiflora possesses antinociceptive, cardiovascular, antioxidant and anti-inflammatory activities.

CONCLUSION

Research shows that D. grandiflora is a potential source of compounds pertaining medicinal applications. It provides an interesting subject in the search for new drugs of natural origin.

Anxiolytic effects of short- and long-term administration of cacao mass on rat elevated T-maze test

We demonstrated the effects of short- and long-term administration of cacao mass on anxiety in the elevated T-maze test, which is an animal model of anxiety. In the first study, we administered cacao mass (100 mg/100 g body weight) per os and immediately performed the elevated T-maze test. Short-term cacao mass significantly abolished delayed avoidance latency compared with the control but did not change escape latency. This result suggested that cacao mass administration reduced conditional fear-relating behavior. Short-term cacao mass administration did not affect the concentration of brain monoamines, emotion-related neurotransmitters such as norepinephrine, serotonin and dopamine, in the rat brain. In the next study, we fed a cacao mass-containing diet to rats for 2 weeks and performed the elevated T-maze test. Contrary to short-term administration, chronic consumption of cacao mass tended to increase avoidance latency and did not change escape latency. Brain serotonin concentration and its turnover were enhanced by chronic consumption of cacao mass. These results suggested that chronic consumption of cacao did not affect fear-related behavior but was involved in brain monoamine metabolism. In conclusion, we suggest that short-term cacao mass consumption showed an anxiolytic effect but chronic consumption did not.

Alprazolam, caffeine and their interaction: relating DRL performance to pharmacokinetics

Three-hour sessions of differential reinforcement of low-rate behavior (DRL 45-s) in rats were used to investigate alprazolam, caffeine, and their interactions at the onset, peak and disappearance of serum alprazolam, while caffeine level remained constant. The dose-response curve (DRC) method of Pöch permitted an extensive evaluation of the kind (additivity or independence) of interactions occurring in combined drug effects. The alprazolam and caffeine DRCs were used to derive theoretical additive and independent relations, and the observed combined effects compared to these functions. Behavior-time profiles of the combined effects were similarly compared. Serum alprazolam and caffeine concentrations correlated with their respective behavior-time profiles. No acute tolerance was observed either for the individual drugs or their combinations. Alprazolam was more potent than caffeine in disrupting DRL behavior. Because alprazolam is much shorter-lived (t1/2 = 32 min) than caffeine (t1/2 = 3 h) in rats, potency ratios between alprazolam and caffeine changed across session time (from 123 to 4), which determined the expression of the combined effects. Although the combined effects were not distinguishable in terms of additivity or independence in both the DRCs and in the behavior-time profiles, they showed neither synergism nor antagonism. The pharmacokinetics of alprazolam were not altered by caffeine, but those of caffeine were affected by alprazolam.

Effects of ethanol, caffeine, and clorazepate on hypertonic NaCl solution intake in rats

Previous reports indicate that several anxiolytics enhance the intake of hypertonic saline in rehydrating rats. This experiment was conducted to determine the effects of repeated (5 sessions) injection (i.p.) of ethanol (0.4 or 0.8 g/kg), caffeine (20 or 40 mg/kg) or clorazepate (3 mg/kg) on the ingestion of hypertonic saline (1.8%) in water-deprived rats. Saline intake increased with the acute administration of both clorazepate and ethanol (two doses), but it decreased with caffeine (two doses). It seems that the increase or decrease of hypertonic saline ingestion following acute drug administration continues to correlate well with anxiolytic or anxiogenic actions. However, following repeated administration of caffeine and ethanol, the effects on saline intake were not maintained in a reliable manner.

Use of Vernonia amygdalina by wild chimpanzee: possible roles of its bitter and related constituents

Bitter principles and related constituents have been isolated from Vernonia amygdalina (Compositae), a plant ingested by wild chimpanzees sometimes suffering from parasite-related diseases in the Mahale Mountains National Park, Tanzania. These isolated constituents were the known sesquiterpene lactones (vernodalin, vernolide, hydroxyvernolide), and new stigmastane-type steroid glucosides (vernonioside A1-A4: for bitter tasting constituents and vernonioside B1-B3; for nonbitter related constituents). Antiparasitic activity tests of these constituents together with quantitative analyses of the major active constituents, vernodalin and vernonioside B1, supported the hypothesis that Mahale chimpanzees control parasite-related diseases by ingesting the pith of this plant, found to contain several steroid-related constituents. While the major active steroid-related constituents (vernonioside B1 and its primary aglycone, vernoniol B1) do not taste bitter themselves, it was hypothesized that the highly bitter constituents including vernodalin may play an important role as signals to the ingester guiding their choice of the appropriate plant, plant part, and possibly also as signals which help to control the amount of intake.

Sustained synergism by chronic caffeine of the motor control deficit produced by midazolam

To evaluate the effects of chronic caffeine on the impairment of discriminative fine motor control produced by midazolam, rats were trained to hold a force transducer steady to deliver food pellets. Chronic, daily doses of midazolam (3 mg/kg SC) led to a stable level of motor impairment. Chronic caffeine (20 mg/kg IP) alone usually produced a more moderate deficit or, for one animal, no deficit. Combined, chronic administration of these doses yielded a sustained synergism in motor performance impairment, which contrasted with the antagonism usually found between the benzodiazepines and methylxanthines when performance is evaluated by psychomotor tests not requiring fine motor control. The observed synergism was not explicable in terms of measured disposition of the drugs. The synergistic production of fine motor dyskinesia by the concurrent administration of caffeine and midazolam may be relevant to the triggering of anxiety attacks by caffeine observed in panic disorder patients.

Synergism by caffeine and by cocaine of the motor control deficit produced by midazolam

To evaluate the effects of caffeine and cocaine on the impairment of discriminative motor control produced by midazolam, rats were trained to hold a force transducer operated with a paw so that it remained between upper and lower limits of a force band for a continuous 1.5-s period to deliver each food pellet. Acute doses of 3 mg/kg midazolam SC impaired motor performance. Except for one animal, caffeine (10-40 mg/kg IP) had little or no effect on performance, while cocaine (3.75-22.5 mg/kg IP) produced dose-related impairment. When each dose of caffeine was combined with 3 mg/kg midazolam, a marked synergism in motor performance impairment occurred. Cocaine plus midazolam produced mainly an additive synergism. The conspicuous synergistic action of caffeine on the motor control deficit produced by midazolam contrasts with the typical antagonism found between the benzodiazepines and methylxanthines when performance is evaluated by psychomotor tests not requiring fine motor control.