Behavioral and molecular actions of caffeine: focus on adenosine

Effect of caffeine on vestibular evoked myogenic potential: a systematic review with meta-analysis

Introduction

Caffeine can be considered the most consumed drug by adults worldwide, and can be found in several foods, such as chocolate, coffee, tea, soda and others. Overall, caffeine in moderate doses, results in increased physical and intellectual productivity, increases the capacity of concentration and reduces the time of reaction to sensory stimuli. On the other hand, high doses can cause noticeable signs of mental confusion and error induction in intellectual tasks, anxiety, restlessness, muscle tremors, tachycardia, labyrinthine changes, and tinnitus.

Objective

Considering that the vestibular evoked myogenic potential is a clinical test that evaluates the muscular response of high intensity auditory stimulation, the present systematic review aimed to analyze the effects of caffeine on vestibular evoked myogenic potential.

Methods

This study consisted of the search of the following databases: MEDLINE, CENTRAL, ScienceDirect, Scopus, Web of Science, LILACS, SciELO and ClinicalTrials.gov. Additionally, the gray literature was also searched. The search strategy included terms related to intervention (caffeine or coffee consumption) and the primary outcome (vestibular evoked myogenic potential).

Results

Based on the 253 potentially relevant articles identified through the database search, only two full-text publications were retrieved for further evaluation, which were maintained for qualitative analysis.

Conclusion

Analyzing the articles found, caffeine has no effect on vestibular evoked myogenic potential in normal individuals.

Nonfatal and fatal intoxications with pure caffeine - report of three different cases

Caffeine is not usually perceived as a drug by most people because it is found in many foods and drinks, including caffeinated energy drinks, as well as in over the counter analgesics and cold preparations. Recently in Poland it has become increasingly common to take pure caffeine, bought through online stores, as a psychoanaleptic. This creates a much higher risk of severe and even fatal poisoning in comparison with the risk associated with the abuse of food products and non-prescription medicines containing low doses of caffeine. This paper presents three different cases of poisoning that occurred when pure caffeine was taken as psychostimulant; in cases 1 and 2 poisoning was the result of a single overdose, while in the case 3 poisoning resulted from a cumulative overdose. In the case 1 there was a severe intoxication (persistent vomiting, hypotension, tremor), and the concentration of caffeine in the blood was found to be 80.16 μg/mL. The patient was treated using hemodialysis, which caused a rapid decrease in blood levels of caffeine and relief of the clinical symptoms of poisoning. Cases 2 and 3 were fatal poisonings, and recorded levels of caffeine in post mortem blood samples were 140.64 μg/mL and 613.0 μg/mL. In case 2 the patient died 10 min after admission to hospital as a result of sudden cardiac arrest, which was preceded by an attack of convulsions, and in case 3 death occurred in home and was also sudden in nature. Taking pure caffeine as a stimulant is associated with a high risk of overdose and the development of serious and even fatal poisoning, and those using pure caffeine are generally completely unaware of these risks. In such cases, death is usually sudden due to functional mechanisms.

The Safety of Ingested Caffeine: A Comprehensive Review

Caffeine is the most widely consumed psychoactive drug in the world. Natural sources of caffeine include coffee, tea, and chocolate. Synthetic caffeine is also added to products to promote arousal, alertness, energy, and elevated mood. Over the past decade, the introduction of new caffeine-containing food products, as well as changes in consumption patterns of the more traditional sources of caffeine, has increased scrutiny by health authorities and regulatory bodies about the overall consumption of caffeine and its potential cumulative effects on behavior and physiology. Of particular concern is the rate of caffeine intake among populations potentially vulnerable to the negative effects of caffeine consumption: pregnant and lactating women, children and adolescents, young adults, and people with underlying heart or other health conditions, such as mental illness. Here, we review the research into the safety and safe doses of ingested caffeine in healthy and in vulnerable populations. We report that, for healthy adults, caffeine consumption is relatively safe, but that for some vulnerable populations, caffeine consumption could be harmful, including impairments in cardiovascular function, sleep, and substance use. We also identified several gaps in the literature on which we based recommendations for the future of caffeine research.

The Influence of Caffeine Arousal on the Frequency of Task-Unrelated Image and Thought Intrusions

Based upon earlier studies relating task-unrelated image and thought (TUIT) frequency to circadian activity levels and to decreases with increased age in adulthood it was hypothesized that increased cortical arousal would result in greater TUIT frequency. In a double-blind study, six young men had arousal induced at two dosages of caffeine, 100 mg and 300 mg. When unintentional and deliberate TUIT frequency at the 100 mg and 300 mg dosages was contrasted with the placebo no significant effects were noted. Change in TUIT frequency between placebo and the 300 mg dosage was significantly correlated with the personality trait of Agreeableness. Lack of compliance, caffeine withdrawal influences, and insufficiently high arousal are discussed as possible sources of the lack of relationship obtained between caffeine dosage and TUIT frequency.

Caffeine Consumption among Adults on Benzodiazepine Therapy: United States 1988–1994

The concomitant use of benzodiazepines and caffeine was studied to learn if caffeine consumption varied as a function of benzodiazepine use. Caffeine may antagonize the effects of benzodiazepine and even relatively small amounts can aggravate symptoms associated with anxiety disorders. In addition, caffeine can cause or aggravate insomnia, one of the main reasons cited for use by the subjects in this analysis. Given this, there would seem to be sufficient reason for at least some users of benzodiazepines to consider, with their physicians, avoiding or limiting caffeine consumption. Data from the Third National Health and Nutrition Examination Survey were analyzed to obtain a nationally representative sample of benzodiazepine users. Subjects included 253 individuals (64% women) whose median age was 54 yr. Approximately 88% of benzodiazepine users reported caffeine consumption in the 24-hr. Dietary Recall. 26% of benzodiazepine users and 23% of nonusers reported consuming greater than 250 mg of caffeine during the 24-hr. reference period. In regression analyses, no significant relationships were found between reported caffeine consumption and benzodiazepine use. This study suggests that users and nonusers of benzodiazepines ingest similar amounts of caffeine even though some users should probably avoid or limit caffeine use.

Caffeine-induced psychiatric manifestations: a review

The association between caffeine consumption and various psychiatric manifestations has long been observed. We present two cases that show the ability of caffeine to induce psychotic and manic symptoms, and we also review the extant literature on caffeine-induced psychiatric manifestations. On the basis of our own and others' findings, we suggest that caffeine may be related to not only de-novo psychotic or mood symptoms but also to aggravation of pre-existing psychotic or mood disorders. We therefore suggest that caffeine consumption among patients with mood or psychotic symptoms should be assessed carefully in clinical practice as part of routine psychiatric evaluations.

Cordycepin Increases Nonrapid Eye Movement Sleep via Adenosine Receptors in Rats

Cordycepin (3′-deoxyadenosine) is a naturally occurring adenosine analogue and one of the bioactive constituents isolated from Cordyceps militaris/Cordyceps sinensis, species of the fungal genus Cordyceps. It has traditionally been a prized Chinese folk medicine for the human well-being. Because of similarity of chemical structure of adenosine, cordycepin has been focused on the diverse effects of the central nervous systems (CNSs), like sleep regulation. Therefore, this study was undertaken to know whether cordycepin increases the natural sleep in rats, and its effect is mediated by adenosine receptors (ARs). Sleep was recorded using electroencephalogram (EEG) for 4 hours after oral administration of cordycepin in rats. Sleep architecture and EEG power spectra were analyzed. Cordycepin reduced sleep-wake cycles and increased nonrapid eye movement (NREM) sleep. Interestingly, cordycepin increased θ (theta) waves power density during NREM sleep. In addition, the protein levels of AR subtypes (A₁, A_2A, and A_2B) were increased after the administration of cordycepin, especially in the rat hypothalamus which plays an important role in sleep regulation. Therefore, we suggest that cordycepin increases theta waves power density during NREM sleep via nonspecific AR in rats. In addition, this experiment can provide basic evidence that cordycepin may be helpful for sleep-disturbed subjects.

Caffeine counteracts impairments in task-oriented psychomotor performance induced by chlorpheniramine: a double-blind placebo-controlled crossover study

This study aimed to evaluate the effects of chlorpheniramine on psychomotor performance and the counteracting effects of caffeine on those sedative antihistamine actions. Sixteen healthy young men participated in this study. Using a double-blind placebo-controlled crossover design, each subject was administered one of the following conditions in a random order with a one-week interval: 'placebo-placebo', '4 mg of chlorpheniramine-placebo', 'placebo-200 mg of caffeine' or '4 mg of chlorpheniramine-200 mg of caffeine'. Before and after the treatments, psychomotor functions were assessed using a battery of tests. Additionally, subjective responses were assessed using a visual analogue scale (VAS). Psychomotor performance changed over time in different ways according to the combination of study medications. In the 'chlorpheniramine-placebo' condition, reaction times of the compensatory tracking task were significantly impaired compared with the other three conditions. In addition, the number of omission errors of the continuous performance test were significantly greater compared with the 'placebo-caffeine' condition. However, the response pattern of the 'chlorpheniramine-caffeine' condition was not significantly different from that of the 'placebo-placebo' condition. Changes of VAS for sleepiness were significantly greater in the 'chlorpheniramine-placebo' condition compared with the other three conditions. In conclusion, chlorpheniramine significantly increases subjective sleepiness and objectively impairs psychomotor performance. However, caffeine counteracts these sedative effects and psychomotor impairments.

Caffeine attenuates metabolic syndrome in diet-induced obese rats

OBJECTIVE

Caffeine is a constituent of many non-alcoholic beverages. Pharmacological actions of caffeine include the antagonism of adenosine receptors and the inhibition of phosphodiesterase activity. The A₁ adenosine receptors present on adipocytes are involved in the control of fatty acid uptake and lipolysis. In this study, the effects of caffeine were characterized in a diet-induced metabolic syndrome in rats.

METHODS

Rats were given a high-carbohydrate, high-fat diet (mainly containing fructose and beef tallow) for 16 wk. The control rats were given a corn starch diet. Treatment groups were given caffeine 0.5 g/kg of food for the last 8 wk of the 16-wk protocol. The structure and function of the heart and the liver were investigated in addition to the metabolic parameters including the plasma lipid components.

RESULTS

The high-carbohydrate, high-fat diet induced symptoms of metabolic syndrome, including obesity, dyslipidemia, impaired glucose tolerance, decreased insulin sensitivity, and increased systolic blood pressure, associated with the development of cardiovascular remodeling and non-alcoholic steatohepatitis. The treatment with caffeine in the rats fed the high-carbohydrate, high-fat diet decreased body fat and systolic blood pressure, improved glucose tolerance and insulin sensitivity, and attenuated cardiovascular and hepatic abnormalities, although the plasma lipid concentrations were further increased.

CONCLUSION

Decreased total body fat, concurrent with increased plasma lipid concentrations, reflects the lipolytic effects of caffeine in adipocytes, likely owing to the caffeine antagonism of A₁ adenosine receptors on adipocytes.

Caffeine increases tear volume depending on polymorphisms within the adenosine A2a receptor gene and cytochrome P450 1A2

PURPOSE

The primary aim of the present study was to examine the effect of caffeine on tear volume. The secondary aim was to investigate the relation between caffeine-induced changes in tear volume and polymorphisms in ADORA2A and CYP1A2.

DESIGN

Double-masked, placebo-controlled, crossover study.

PARTICIPANTS

Seventy-eight healthy volunteers were recruited for the study.

METHODS

Subjects participated in 2 sessions in which they received capsules containing either placebo or caffeine. The caffeine capsules were given to the subjects to keep the caffeine volume per body weight within 5 to 7 mg/kg. After caffeine intake, tear meniscus height (TMH) was measured. Subjects provided a blood sample for genotyping.

MAIN OUTCOME MEASURES

Tear meniscus height, single nucleotide polymorphism.

RESULTS

The tear volume increased after caffeine consumption. The net increase in TMH was 0.08 mm (95% confidence interval, 0.05-0.10) greater when participants were given caffeine than when given placebo (P<0.0001). In ADORA2A, the difference in the net increase in TMH for participants who were heterozygous at rs5751876 and rs2298383 was 0.07 mm (P = 0.001) and who were minor homozygous was 0.08 mm (P = 0.007). In CYP1A2, the net increase in TMH for participants who were minor homozygous at rs2472304 was lower than for those who were major homozygous; the difference was 0.06 mm (P = 0.039).

CONCLUSIONS

Caffeine intake increases tear volume and polymorphisms within ADORA2A, and CYP1A2 is associated with the tear increase after caffeine intake. Genetic polymorphisms had a significant effect on tear meniscus that was of limited clinical significance.

Winning a won game: caffeine panacea for obesity syndemic

Over the past decades, chronic sleep reduction and a concurrent development of obesity have been recognized as a common problem in the industrialized world. Among its numerous untoward effects, there is a possibility that insomnia is also a major contributor to obesity. This attribution poses a problem for caffeine, an inexpensive, “natural” agent that is purported to improve a number of conditions and is often indicated in a long-term pharmacotherapy in the context of weight management. The present study used the “common target” approach by exploring the tentative shared molecular networks of insomnia and adiposity. It discusses caffeine targets beyond those associated with adenosine signaling machinery, phosphodiesterases, and calcium release channels. Here, we provide a view suggesting that caffeine could exert some of its effects by acting on several signaling complexes composed of HIF-1α/VEGF/IL-8 along with NO, TNF-α, IL1, and GHRH, among others. Although the relevance of these targets to the reported therapeutic effects of caffeine has remained difficult to assess, the utilization of caffeine efficacies and potencies recommend its repurposing for development of novel therapeutic approaches. Among indications mentioned, are neuroprotective, nootropic, antioxidant, proliferative, anti-fibrotic, and anti-angiogenic that appear under a variety of dissimilar diagnostic labels comorbid with obesity. In the absence of safe and efficacious antiobesity agents, caffeine remains an attractive adjuvant.

Depressing effects of caffeine at crayfish neuromuscular synapses I. Dosage response and Ca++ gradient effects

The response of crayfish synaptic terminals to drugs began to be studied to characterize the terminal's physiological characteristics. Caffeine, the first drug to be studied, was selected to enhance synaptic transmission because of its ability to increase calcium release from internal stores.1. The largest excitor neuron to the superficial flexor muscle system of Procambarus clarkii was stimulated at 10 Hz while recording junction potentials from several lateral muscle fibers.2. Caffeine unexpectedly decreased synaptic transmission in this system in a dosage-dependent manner. The depressing effect of caffeine was observed at 5 mM caffeine and junction potentials disappeared completely at 50 mM. Washing the preparation in fresh control Ringers did not restore the amplitudes of the junction potentials.3. Changes in extracellular calcium concentrations delayed or depressed the caffeine effect depending on the calcium gradient across the membrane or the caffeine dosage. The data suggest that calcium is involved in caffeine's response in this system in a way yet to be determined.

Depressing Effect of Caffeine at Crayfish Neuromuscular Synapses II. Initial Search for Possible Sites of Action

Caffeine's unexpected depression of synaptic transmission in the superficial flexor muscle system (SFM) of Procambarus clarkii was studied by looking at three known sites of action of this drug: via adenosine and ryanodine receptors and inhibition of phosphodiesterase.1. JPs did not change in size when exposed to physiological concentrations of adenosine, suggesting that the SFM system lacks presynaptic adenosine receptors.2. JPs slightly increased in size in the presence of a phosphodiesterase inhibitor, the opposite response to that obtained with caffeine, suggesting that caffeine is not acting via this pathway.3. A calcium ionophore immediately enhanced synaptic transmission in the SFM system but when given in combination with caffeine the enhancement is reduced and declines over time.4. Serotonin enhanced synaptic transmission in the SFM system, but when given in combination with caffeine this enhancement was not observed.5. These caffeine effects are interpreted in terms of alterations to the calcium homeostatic mechanisms of the terminals.

Effects of adenosine on gabaergic synaptic inputs to identified ventrolateral preoptic neurons

The ventrolateral preoptic nucleus (VLPO) is a key regulator of behavioral state that promotes sleep by directly inhibiting brain regions that maintain wakefulness. Subarachnoid administration of adenosine (AD) or AD agonists promotes sleep and induces expression of Fos protein in VLPO neurons. Therefore, activation of VLPO neurons may contribute to the somnogenic actions of AD. To define the mechanism through which AD activates VLPO neurons, we prepared hypothalamic slices from 9 to 12-day-old rat pups and recorded from 43 neurons in the galaninergic VLPO cluster; nine neurons contained galanin mRNA by post hoc in situ hybridization. Bath application of AD (20 microM) to seven of these neurons had no direct effect but caused a significant decrease in the frequency of spontaneous miniature inhibitory postsynaptic currents in the presence of tetrodotoxin, indicating a presynaptic site of action. We conclude that AD-mediated disinhibition increases the excitability of VLPO neurons thus contributing to the somnogenic properties of AD.

Association between A2a receptor gene polymorphisms and caffeine-induced anxiety

The adenosine receptor system, which mediates the psychoactive effects of caffeine, is also thought to be involved in the regulation of anxiety. In this study, we examined the association between variations in anxiogenic responses to caffeine and polymorphisms in the A1 and A2a adenosine receptor genes. Healthy, infrequent caffeine users (N=94) recorded their subjective mood states following a 150 mg oral dose of caffeine freebase or placebo in a double-blind study. We found a significant association between self-reported anxiety after caffeine administration and two linked polymorphisms on the A2a receptor gene, the 1976C>T and 2592C>Tins polymorphisms. Individuals with the 1976T/T and the 2592Tins/Tins genotypes reported greater increases in anxiety after caffeine administration than the other genotypic groups. The study shows that an adenosine receptor gene polymorphism that has been associated with Panic Disorder is also associated with anxiogenic responses to an acute dose of caffeine.

Caffeine raises the serum melatonin level in healthy subjects: an indication of melatonin metabolism by cytochrome P450(CYP)1A2

Caffeine is metabolized in the liver by cytochrome P450(CYP)1A2. Recent findings imply that this enzyme may also be of importance for the metabolism of human melatonin (MT). If caffeine and MT are metabolized by the same enzyme, one may expect to find different serum MT levels after ingestion of coffee compared with placebo. Although coffee is consumed by people all over the world, few studies have focused on whether caffeine actually affects serum MT levels in normal subjects. We decided to study that particular topic. For that purpose 12 healthy individuals were tested on two occasions, one week apart. On one of these occasions they were given a capsule containing 200 mg caffeine in the evening. On the other, they received placebo. The experimental order was randomized. Serum MT levels were determined every second hour between 22:00 h and 08:00 h, and the melatonin areas under the curve (MT-AUCs) were calculated. After caffeine the serum MT level rose from 0.09 +/- 0.03 nmol/l at 22:00 h to 0.48 +/- 0.07 nmol/l at 04:00 h. The corresponding rise after placebo was less prominent (from 0.06 +/- 0.01 to 0.35 +/- 0.06 nmol/l). This was reflected by the MT-AUC which was 32% larger after ingestion of caffeine compared with placebo (MT-AUC(caffeine) 3.16 +/- 0.44 nmol/l x h vs MT-AUC(placebo) 2.39 +/- 0.40 nmol/l x h; p < 0.02). These findings imply that caffeine, ingested in the evening at a dose corresponding to two ordinary cups of coffee, augments the nocturnal serum MT level, which in turn supports the notion that cytochrome P450(CYP)1A2 is involved in the hepatic metabolism of human MT.

Effects of caffeine on human health

Caffeine is probably the most frequently ingested pharmacologically active substance in the world. It is found in common beverages (coffee, tea, soft drinks), in products containing cocoa or chocolate, and in medications. Because of its wide consumption at different levels by most segments of the population, the public and the scientific community have expressed interest in the potential for caffeine to produce adverse effects on human health. The possibility that caffeine ingestion adversely affects human health was investigated based on reviews of (primarily) published human studies obtained through a comprehensive literature search. Based on the data reviewed, it is concluded that for the healthy adult population, moderate daily caffeine intake at a dose level up to 400 mg day(-1) (equivalent to 6 mg kg(-1) body weight day(-1) in a 65-kg person) is not associated with adverse effects such as general toxicity, cardiovascular effects, effects on bone status and calcium balance (with consumption of adequate calcium), changes in adult behaviour, increased incidence of cancer and effects on male fertility. The data also show that reproductive-aged women and children are 'at risk' subgroups who may require specific advice on moderating their caffeine intake. Based on available evidence, it is suggested that reproductive-aged women should consume </=300 mg caffeine per day (equivalent to 4.6 mg kg(-1) bw day(-1) for a 65-kg person) while children should consume </=2.5 mg kg(-1) bw day(-1).

Caffeine consumption and weekly sleep patterns in US seventh-, eighth-, and ninth-graders

OBJECTIVE

To survey caffeine use by seventh-, eighth-, and ninth-graders and relate its use to age, sex, sleep characteristics, and day of week

METHODS

Students kept a daily, 2-week diary of their sleep times and use of caffeine containing drinks and foods. Data were analyzed by fitted multiple regression models

RESULTS

A total of 191 students participated. Caffeine intake ranged between 0 and 800 mg/d. Mean use over 2 weeks ranged up to 379.4 mg/d and averaged 62.7 mg/d (corrected for underrepresentation in our sample of boys, who consumed more caffeine). Higher caffeine intake in general was associated with shorter nocturnal sleep duration, increased wake time after sleep onset, and increased daytime sleep. SLEEP PATTERNS: Mean bedtime was 10:57 PM, and mean wake time was at 7:14 AM. Older children delayed bedtime longer on weekends, and younger ones had longer nightly sleep durations. Sleep duration lengthened on weekends, reflecting the combined effects of the circadian timing system and a mechanism that regulates the duration of sleep. Caffeine (soda) consumption also increased on weekends, for reasons that may be primarily social

CONCLUSIONS

Regardless of whether caffeine use disturbed sleep or was consumed to counteract the daytime effect of interrupted sleep, caffeinated beverages had detectable pharmacologic effects. Limitation of the availability of caffeine to teenagers should therefore be considered.

Effects of caffeine on human behavior

The literature suggests that the following effects on behavior of adult humans may occur when individuals consume moderate amounts of caffeine. (1) Caffeine increases alertness and reduces fatigue. This may be especially important in low arousal situations (e.g. working at night). (2) Caffeine improves performance on vigilance tasks and simple tasks that require sustained response. Again, these effects are often clearest when alertness is reduced, although there is evidence that benefits may still occur when the person is unimpaired. (3) Effects on more complex tasks are difficult to assess and probably involve interactions between the caffeine and other variables which increase alertness (e.g. personality and time of day). (4) In contrast to the effects of caffeine consumption, withdrawal of caffeine has few effects on performance. There is often an increase in negative mood following withdrawal of caffeine, but such effects may largely reflect the expectancies of the volunteers and the failure to conduct "blind" studies. (5) Regular caffeine usage appears to be beneficial, with higher users having better mental functioning. (6) Most people are very good at controlling their caffeine consumption to maximise the above positive effects. For example, the pattern of consumption over the day shows that caffeine is often consumed to increase alertness. Indeed, many people do not consume much caffeine later in the day since it is important not to be alert when one goes to sleep. In contrast to effects found from normal caffeine intake, there are reports that have demonstrated negative effects when very large amounts are given or sensitive groups (e.g. patients with anxiety disorders) were studied. In this context caffeine has been shown to increase anxiety and impair sleep. There is also some evidence that fine motor control may be impaired as a function of the increase in anxiety. Overall, the global picture that emerges depends on whether one focuses on effects that are likely to be present when caffeine is consumed in moderation by the majority of the population or on the effects found in extreme conditions. The evidence clearly shows that levels of caffeine consumed by most people have largely positive effects on behavior. Excessive consumption can lead to problems, especially in sensitive individuals.

Herbal Medicines and Epilepsy: The Potential for Benefit and Adverse Effects

The widespread availability and use of herbal medicines raise the potential for adverse effects in the epilepsy population. Herbal sedatives (kava, valerian, chamomile, passionflower) may potentiate the effects of antiepileptic medications, increasing their sedative and cognitive effects. Despite some antiseizure effects in animal models, they should not be used in place of standard seizure medications because efficacy has not been established. Anecdotal, uncontrolled observations suggest that herbal stimulants containing ephedrine (ephedra or ma huang) and caffeine (cocoa, coffee, tea, maté, guarana, cola or kola) can exacerbate seizures in people with epilepsy, especially when taken in combination. Ginkgo and ginseng may also exacerbate seizures although the evidence for this is similarly anecdotal and uncertain. St. John's wort has the potential to alter medication pharmacokinetics and the seizure threshold. The essential oils of many plants contain epileptogenic compounds. There is mixed evidence for evening primrose and borage lowering the seizure threshold. Education of both health care providers and patients is the best way to avoid unintentional and unnecessary adverse reactions to herbal medicines.

Escape deficits induced by inescapable shock and metabolic stress are reversed by adenosine receptor antagonists

We examined the relationship between metabolic stress, brain adenosine regulation, and the learned helplessness effect in four experiments in rats. Glucoprivation and metabolic inhibition were induced by treating previously restrained (nonshocked) rats with 2-deoxy-D-glucose (2DG) shortly before escape testing. Experiment 1 demonstrated that 2-deoxy-D-glucose impairs escape performance in a dose-dependent manner. Experiment 2 showed that 2-deoxy-D-glucose and shock induced escape deficits are completely reversed by peripheral administration of the adenosine receptor antagonist caffeine. This result indicates that both inescapable shock and 2-deoxy-D-glucose result in compensatory adenosine regulation which, in turn, mediates the behavioral impairment. Experiment 3 determined that 8-[p-sulfophenyl]-theophylline, a peripheral adenosine receptor antagonist, fails to reverse the escape deficit resulting from metabolic stress, whereas centrally acting theophylline does. Experiment 4 showed that the behavioral impairments from both 2-deoxy-D-glucose and inescapable shock are reversed by intracranial ventricular (icv) caffeine treatment. The results of Experiments 3 and 4 indicate that the enhanced adenosine regulation and the ensuing performance deficit resulting from 2-deoxy-D-glucose treatment occurred in the central nervous system. These data are discussed in terms of the metabolic demands of neuronal over-activation during escape testing in inescapably shocked rats and the loss of normal behavioral function due to compensatory adenosine regulation in the brain.

Can Prenatal Caffeine Exposure Affect Behavioral Inhibition?

Given the widespread use of caffeine and its potential nonoptimal effects during pregnancy, it is remarkable and distressing that almost nothing is known about the long-term effects of prenatal caffeine exposure in humans. Research on nonhumans reveals that prenatal caffeine exposure is associated with an enduring tendency toward a profile of fearfulness, hypoactivity, and exaggerated stress in uncertain situations. A similar pattern of behavioral inhibition has been observed in humans and has been attributed to various causes such as inborn temperament or environmental influences. The author's conjecture is that prenatal caffeine exposure could be an additional factor contributing to the tendency toward behavioral inhibition. One mechanism for this effect is that caffeine causes an upregulation of adenosine receptors, thus creating a vulnerability to adenosine-induced inhibition of neuronal firing and neurotransmitter release.

CCK4-induced panic in healthy subjects II: neurochemical correlates

Cholecystokinin tetrapeptide (CCK4) induces symptoms similar to those of panic attack. The present study investigated the effects of CCK4 administration on catecholaminergic system. In this double blind, randomised, crossover experiment, 16 healthy subjects received injections of either 25 microg of CCK4 or placebo on two separate occasions. Platelet and plasma catecholamine concentrations were assessed before the administration and compared to post-injection values. The results clearly show that both plasma and platelet concentrations of catecholamines are significantly affected by CCK4. Plasma norepinephrine (NE) and epinephrine (EPI) raised significantly above baseline in the immediate post-CCK4 period, while in plasma dopamine (DA), the significant increases were delayed. In the platelets, significant post-CCK4 increases of NE and EPI concentrations were observed with a delay of several minutes. In summary, we have demonstrated that, in healthy subjects, CCK4 increases peripheral concentrations of catecholamines in both plasma and platelets, with the most consistent changes occurring in platelet NE and plasma EPI concentrations.

Pharmacologic management of postdural puncture headache

OBJECTIVE

To discuss the pathogenesis, incidence, and clinical presentation of postdural puncture headaches (PDPHs) and to provide a comprehensive evaluation on the pharmacologic management of PDPH.

DATA SOURCE

A MEDLINE search was used to identify pertinent literature published in English including review articles, case reports, letters, and abstracts. Information was also extracted from textbooks for background purposes.

STUDY SELECTION

All clinical studies, case reports, abstracts, and letters were included because of the limited amount of literature available on the pharmacologic therapy for PDPH. Related research articles and review articles were also used to provide background information on PDPH.

DATA EXTRACTION

Methodology and results from clinical trials and abstracts were described and evaluated. Case reports and letters were summarized and critically reviewed for the feasibility of the different treatment modalities. Information on the pathophysiology, incidence and severity, and clinical presentation of PDPH was extracted from related research articles, review articles, and textbooks.

DATA SYNTHESIS

The epidural blood patch (EBP) is one of the most effective treatments for PDPH. Pharmacologic management of PDPH offers a less invasive treatment modality than the EBP. Numerous drug therapies have been presented in the literature, though few merit clinical application. Caffeine therapy, both oral and parenteral, is the most commonly used pharmacologic treatment modality. Theophylline and sumatriptan are potentially promising agents for the treatment of PDPH. Epidural administration of fluids and drugs is also effective in the treatment of PDPH. Epidural adrenocorticotropic hormone and epidural morphine also demonstrate some potential in the treatment of PDPH. Individual patient characteristics (i.e., HIV, sepsis) need to be considered when deciding on a treatment. More reports, especially clinical studies, are necessary before a definitive statement can be made regarding any one treatment. In the meantime, therapy will be guided by clinical judgement based on the literature reviewed in this article.

CONCLUSIONS

Intravenous and oral caffeine are effective and noninvasive treatments for PDPH. Epidural NaCl 0.9% or dextran are alternatives when the EBP is unsuccessful or contraindicated. Several methods of pharmacologic management have been cited in the literature, but all require further evaluation.

Effects of diazepam and cyclohexyladenosine on open-field behavior in rats perinatally exposed to caffeine

Adult rat offspring earlier exposed to maternally ingested caffeine during both gestation and lactation were observed in an open field following acute administration of diazepam or cyclohexyladenosine. While both drugs reduced measures of locomotion and emotional reactivity, caffeine-exposed rats showed evidence of greater sensitivity to cyclohexyladenosine (but not diazepam) as determined by its effects on grooming behavior and tendencies to occupy the center squares of the apparatus. This suggested that adenosine (A1) rather than benzodiazepine receptor activity had been affected by the perinatal caffeine experience which also reduced locomotor activity while increasing center occupancy. The acute effects of diazepam and cyclohexyladenosine also depended largely on the sex of the subjects. Diazepam affected locomotor activity more and both drugs affected defecation less in females than in males. No other interaction involving sex was significant.

The effects of different doses of caffeine on habituation of the human acoustic startle reflex

Research in this laboratory showed that caffeine (4 mg/kg) delays habituation of the acoustic startle reflex in humans. The present study examined the effects of 2- and 6-mg/kg doses of caffeine on acoustic startle habituation in moderate-high and low caffeine users. Eyeblink responses to 30 trials of 85-dB noise stimuli were measured beginning 30 min after oral ingestion of either placebo or 2 or 6 mg/kg of caffeine. The 2-mg/kg dose of caffeine delayed startle habituation in both moderate-high and low caffeine users. The 6-mg/kg dose produced no differential effects on startle responding from placebo. In moderate-high users, following habituation, startle responding was smaller in the placebo condition compared to both caffeine conditions. In low users there were no differences in posthabituation responding between doses, suggesting that this dose effect is dependent on a history of chronic caffeine usage.

Effects of theophylline on nocturnal sleep and daytime sleepiness/alertness

To study the short-term effects of theophylline on sleep and wakefulness, 24 healthy men and women, aged 21 to 35 years, received each of three doses, 0, 3, and 6 mg/kg, of theophylline double-blind in a Latin Square design, administered to 12 subjects at 9 AM and to the other 12 at 11 PM. After the daytime administration, sleep latency was tested at 10 AM, 12 Noon, 2 PM, and 4 PM and divided attention and auditory vigilance performance were tested at 10:30 AM and 2:30 PM. After the nighttime administration, a standard 8-h polysomnogram was collected. On a separate day all subjects received a single 6-mg/kg dose at 9 AM and blood samples were drawn at 8:30 and 10:30 AM, 12:30 PM, 2:30 PM, and 4:30 PM. The serum theophylline levels for the 6-mg/kg dose peaked at 11.0 micrograms/mL and declined to 8.1 micrograms/mL by 4:30 PM. In the daytime administration, daytime mean sleep latency was increased by both doses and performance was improved by the high dose but not the low dose. In the nighttime administration, nocturnal sleep onset was delayed and total wake time was increased by the high dose but not the low dose. The low dose increased the amount of light stage 1 sleep without producing wakefulness.

Reduced proconvulsant activity of caffeine in rats after a series of electroconvulsive seizures

A variety of neurotransmitter receptor changes occur after a course of electroconvulsive seizures (ECS) in rats, including an increased density of adenosine A1 sites. Adenosine antagonism has been related to the proconvulsant action of methylxanthines such as caffeine. We determined tonic-clonic seizure duration in rats given ECS with caffeine (0-175 mg/kg, IP) after a course of one or six daily ECS. A single day of ECS did not affect the dose-dependent proconvulsant action of caffeine. After six daily ECS, the proconvulsant action of caffeine was reduced. After nine daily ECS, an A1 antagonist (8-cyclopentyl-1,3-dipropylxanthine) and an A2A antagonist (1-allyl-3,7-dimethyl-8-p-sulfophenylxanthine) showed reduced proconvulsant activity. The results suggest that the reduced proconvulsant action of caffeine after chronic ECS depends on adenosine antagonism.

Post-dural puncture thoracic pain without headache: relief with epidural blood patch

We report two unusual cases of postural, post-dural puncture upper thoracic interscapular backache, without headache, that were relieved by epidural blood patching. There is controversy concerning the aetiology of headache associated with the post-dural puncture syndrome. Mechanisms previously proposed have included traction on pain-sensitive intracranial structures such as the dura or blood vessels, or a vascular mechanism which may be adenosine-receptor mediated. These two cases suggest that traction on cervical or upper thoracic nerve roots should be considered as a possible mechanism of pain in the post-dural puncture syndrome.

Determination of a new antibronchospastic agent, MX2/120, in guinea pig plasma by high-performance liquid chromatography in a pharmacokinetic study

7-[(2,2-Dimethyl)propyl)]-1-methylxanthine (I, Lab code MX2/120) is a new potent antibronchospastic agent. A rapid and simple HPLC assay for I in guinea pig plasma has been developed. Compound I was extracted from plasma with dichloromethane by a solid-phase extraction procedure, after adding 1,3-dimethyl-7-pentylxanthine at a concentration of 5 micrograms/ml as the internal standard (I.S.). The extraction residue was redissolved in water-acetonitrile and chromatographed on a RP-18 reversed-phase column. The eluate was monitored by spectrophotometric detection at 280 nm. The method showed good linearity over the range 0.1-20 micrograms/ml (r = 0.9998) and is precise (C.V. x Student's t-test = 1.84%) and accurate (mean recovery +/- limit of confidence = 100.25 +/- 0.34). The HPLC assay was successfully applied to the determination of the pharmacokinetic profile of I after intravenous and oral administration in guinea pigs. The main pharmacokinetic parameters are presented.

Effects of neonatal exposure to caffeine on adenosine A1 receptor ontogeny using autoradiography

The ontogeny of adenosine A1 receptor density was assessed via autoradiographical analysis of [3H]cyclohexyladenosine ([3H]CHA) binding in brains of 14-31-day-old rats as a function of exposure to caffeine over postnatal days 2-6. This exposure period was analogous to the period during which human infants are administered caffeine as treatment for apnea of prematurity. [3H]CHA binding was greatest in CA1 and CA3 hippocampus in both caffeine-exposed and control rats across all ages. Within the anterior, ventral, lateral and medial regions of the thalamus of unmanipulated rats, [3H]CHA binding did not change with age. In caffeine-exposed rats, however, [3H]CHA binding increased significantly within these thalamic subregions as the rats aged. In addition, with age in both treatment groups, the molecular and granular layers of the cerebellum and the CA1 and dentate gyrus of the hippocampus displayed increasing [3H]CHA density. Furthermore, regardless of age, [3H]CHA binding was decreased in the molecular layer of neonatally caffeine-exposed animals as compared to controls. Thus, limited exposure to caffeine within the first postnatal week altered the subsequent expression of adenosine A1 receptors in most subregions of the thalamus and in the molecular layer of the cerebellum.

The effect of dietary caffeine manipulation on blood caffeine, sleep and disturbed behaviour

The effect of withdrawal of caffeine from the diet of a group of highly disturbed severely retarded adult patients was studied. Two weeks withdrawal produced no improvement in sleep pattern or behaviour, but re-introduction of normal diet was accompanied by a highly significant increase (P < 0.001) in ward disturbance ratings.

The effects of the purinergic system on digitalis-induced epileptiform activity

It has been suggested that endogenous chemical substances, such as adenosine, released during a seizure attack, may act as anticonvulsants in vivo. We have investigated electrophysiologically the effects of purinoceptor agonists and antagonists on the epileptiform activity induced by intracortical digitalis in anesthetized rats. Intracortical injections of 1, 2, or 4 micrograms digitalis (desacetyl lanatocid C) caused an epileptiform electrocorticogram (ECoG). The application of adenosine (25 or 100 microM) or adenosine triphosphate (ATP) (3 mM) after desacetyl lanatocid C blocked the epileptiform activity. beta, gamma-Methylene ATP (0.1-0.8 mM), a stable analog of ATP, produced inhibition and then death. The epileptogenic effect of desacetyl lanatocid C was enhanced by theophylline (1 mM); however, suramin (1 mM) changed the pattern of epilepsy. These results indicate that the purinergic system may be involved in the mechanism of action of digitalis glycosides.

Dose-response effects of intravenous caffeine in normal volunteers

The administration of caffeine has been developed as a chemical model for the study of anxiety. However, previous researchers investigating caffeine-induced anxiety states in humans have administered oral caffeine. In this dose-response study, we investigated the effects of blindly administered intravenous caffeine (3, 5, and 7 mg/kg) versus placebo in normal control subjects. We report the first series of subjects experiencing olfactory hallucinations (10 of 10 subjects, 24 of 30 infusions) immediately following intravenous caffeine infusion. In addition, consistent with our previous work with oral caffeine, we found dose-related increases in ratings of anxiety and blood levels of cortisol and lactate. One subject experienced a DSM-III-R panic attack. Further questioning revealed that his mother suffers panic attacks. Our findings of olfactory hallucinations are discussed within the context of localized limbic system dysfunction, noting the phenomenologic and possible neuroanatomic overlap between panic disorder and complex partial seizures.

Immunohistochemical localisation of the 90, 70 and 25 kDa heat shock proteins in control and caffeine treated rat embryos

Human and animal experimental data demonstrate that in utero exposure to caffeine results in intrauterine growth retardation and long-term behavioural and reproductive effects. We have suggested that the disruption of normal transcription and translation associated with the initiation of the heat shock response may be a possible mechanism of action of caffeine. This hypothesis was investigated using immunohistochemistry to determine whether an acute (3 h) dose of 30 mg/kg caffeine alters the distribution of hsp 90, 70 and 25 in 10.5-12.5 g.d. rat embryos. In the control embryos hsps 90 and 70 were distributed throughout the embryo with no areas of specific accumulation. Hsp 25 was localised to the developing myocardium of 10.5, 11.5 and 12.5 g.d. embryos and the myotome of 11.5 and 12.5 g.d. embryos. The appearance of hsp 25 was correlated with the onset of muscle fibre differentiation and it is suggested that hsp 25 is associated with cytoskeletal proteins. Following dosing with caffeine no change in the distribution of staining for hsp 90, 70 and 25 was found. These results strongly suggest that caffeine's mechanism of action does not involve initiation of the heat shock response.

Lack of efficacy of the adenosine reuptake inhibitor dipyridamole in the treatment of anxiety disorders

We administered dipyridamole, an adenosine reuptake inhibitor, to 12 outpatients with DSM-III-R anxiety disorders (2 patients with generalized anxiety disorder, 10 patients with panic disorder). Dipyridamole was administered at a flexible dose in a single-blinded fashion following a placebo washout phase and elimination of placebo responders. The mean duration of active treatment with dipyridamole was 46 days (range 21-88 days); the mean peak dose of dipyridamole was 202 +/- 55 mg/day (range 100-300 mg/day). Symptom ratings were completed at regular intervals by the patient and by a research nurse unaware of the treatment condition. Clinically significant improvement in anxiety symptoms was not demonstrated. The implications of these findings for an adenosinergic dysfunction model of panic disorder are discussed.

The effects of caffeine and evening meals on sleep and performance, mood and cardiovascular functioning the following day

An experiment was carried out to examine the effects of caffeine and evening meals on sleep and performance, mood and cardiovascular functioning in the early morning of the next day. Forty-eight subjects were assigned to one of the four conditions formed by combining caffeine and meal conditions. Subjects in the caffeine condition were given 3 mg/kg caffeine in de-caffeinated coffee. The caffeine manipulation was double blind. Subjects in the meal condition were given a 3-course meal (∼ 1300 calories). Sleep was assessed by subjective ratings and these showed that both caffeine and consumption of the meal influenced sleep, but that there were no interactions between caffeine and meal conditions. Although caffeine disrupted sleep there was no evidence of performance or mood being impaired the next day. However, blood pressure was still higher the next day in subjects given caffeine the previous evening.

Caffeine effects on meiotic maturation in hamster oocytes in vitro

The effect of caffeine on meiotic maturation in cultured hamster oocytes was investigated. Meiotic status was scored from chromatin spreads of oocytes previously exposed to caffeine (0, 0.00017, 0.0017, 0.017, 0.17, 1.7, 2.4, 5.1, and 10.2 mM) for up to 20 h. While concentrations of caffeine less than 0.017 mM failed to affect significantly the onset of meiotic resumption, 0.0017 mM caffeine significantly decreased the proportion of oocytes progressing normally to telophase I-metaphase II, and concomitantly increased the proportion of both diploid MII and aneuploid oocytes. In addition, 0.17 to 10.2 mM caffeine induced a dose-dependent increase in the proportion of meiotically arrested oocytes, with less than 5% oocytes progressing normally through to the final stages of meiotic maturation at 10.2 mM caffeine. Taken together, these data show that caffeine at concentrations as low as 0.0017 to 0.017 mM interfere with progression of meiotic maturation, and that concentrations higher than 0.017 mM delay initiation of this process. Since caffeine peaks at 0.017 mM in the plasma of women following a cup of brewed coffee, we conclude that caffeine-induced perturbations of oocyte meiotic maturation may be responsible, at least in part, for the recently revealed correlation between caffeine intake and reduced fertility in women.

Potentiation of cocaine and d-amphetamine toxicity with caffeine

The effect of caffeine when combined with cocaine or amphetamine was studied in rats. Animals were pretreated with intraperitoneal vehicle (normal saline [NS]) or caffeine 100 mg/kg, then challenged with intraperitoneal cocaine (0, 35, 50, 70, or 90 mg/kg) or intraperitoneal d-amphetamine (0, 15, 25, 35, or 42 mg/kg). Animal behavior, time to, and incidences of seizures and death were recorded. This dose of caffeine alone did not cause seizures or death. Caffeine pretreatment significantly increased the incidence of overt seizures induced by either cocaine or amphetamine. Caffeine increased the incidence of cocaine-induced death from 10% to 90% at the 70 mg/kg cocaine dose (P less than .01). Caffeine increased amphetamine-induced death from 0% to 80% at 15 mg/kg (P less than or equal to .01), 10% to 70% at 25 mg/kg (P less than or equal to .01), and 30% to 80% at 35 mg/kg (P less than or equal to .01). To investigate mechanisms, additional animals were pretreated with the adenosine agonist, 2-chloroadenosine (2.5 and 10 mg/kg), before being challenged with NS, 90 mg/kg cocaine, or 42 mg/kg amphetamine. Pretreatment with 2-chloroadenosine had no affect in reducing cocaine or amphetamine toxicity. Combination pretreatment with caffeine and 2-chloroadenosine potentiated cocaine toxicity. The phosphodiesterase inhibitor, pentoxifylline, did not potentiate cocaine toxicity. The authors conclude that caffeine potentiates the acute toxicity of both cocaine and amphetamine, and that the failure of 2-chloroadenosine to alter this suggests that the toxicity of the stimulants cocaine and amphetamine may be modulated by nonspecific rather than specific adenosine- or phosphodiesterase-induced mechanisms.

The tottering mouse: a critical review of its usefulness in the study of the neuronal mechanisms underlying epilepsy

The tottering mouse resulted from a recessively inherited, autosomal, single-locus mutation which produces a very characteristic neurological and cellular phenotype. Almost simultaneously and late in the development of this mutant appears a triad of symptoms: frequent episodes of absence seizures with spike-and-wave discharges; more rarely occurring episodes of focal motor seizures; and ataxia. Electrographic, behavioural and pharmacological similarities to absence epilepsy in man make the tottering mouse a useful animal model for testing new anti-absence drugs. It also affords a unique opportunity to study the effects of multiple alleles on epileptic behaviour. The neuronal mechanisms underlying the generation of absence seizures in this mutant are apparently a combination of a generalized noradrenergic hyperactivity in the brain and some gene-linked, but unknown, conditions prevailing in an earlier phase of development at specific brain areas which induce the generalized forebrain hyper-innervation by locus coeruleus terminals. Several biochemically, microscopically and electrophysiologically identified cellular differences between normal and tottering mice are potential aspects of this primary developmental defect. Research into these gene-linked neuronal characteristics co-inherited with seizures in this mutant makes the tottering mouse a powerful tool in the study of cellular mechanisms underlying genetically determined factors in epileptogenesis.

Effects of single and repeated doses of theophylline on aspects of performance, electrophysiology and subjective assessments in healthy human subjects

The effects of both single and repeated doses of theophylline were evaluated on a battery of nine performance tests, the EEG, the EMG and on subjective assessments of mood and side-effects. The subjects were 20 healthy adults who participated in both phases of this randomized, double-blind, placebo controlled, crossover study. The single dose of 400 mg and the repeated doses of 300 mg b.d. for 4 weeks were intended to attain therapeutic serum concentrations. The Sternberg Additive Factors Method for assessing information processing revealed enhanced performance in both phases of this study, while the Horizontal Addition Test showed improved performance in the single dose phase only. The remaining seven performance tests failed to show significant differences between theophylline and placebo. Single doses of theophylline did not significantly alter mood, but marked adverse effects were encountered in the repeated dose phase, possibly related to unpleasant side-effects. Both EEG and EMG findings indicative of stimulation were associated with a single dose of theophylline, but substantial tolerance developed during 4 weeks of therapy. These findings demonstrate CNS stimulation by both single and repeated doses of theophylline with the occurrence of adverse side-effects during repeated administrations.

Neonatal caffeine exposure alters developmental sensitivity to adenosine receptor ligands

Studies were done to determine whether the apparent changes in behavioral sensitivity to adenosine receptor ligands that occur with age and with neonatal caffeine exposure were due to a change in sensitivity of the receptor for the ligand or to a more fundamental change in the receptor. Using an animal model that mimics the brain developmental period and level of caffeine exposure in human premature neonates treated with caffeine for apnea of prematurity, behavioral and neurochemical investigations were undertaken. The locomotor responses to acute challenge with caffeine (15, 30 and 60 mg/kg) and with D-phenylisopropyladenosine (D-PIA) (0.038 and 0.38 mg/kg), an adenosine receptor agonist, were measured in control and neonatally caffeine-exposed rats at 12, 15, 18, and 28 days of age. The dissociation constants (Kd) and maximal binding densities (Bmax) for agonist binding at the adenosine A1 receptor site were determined over a similar time period. Caffeine displacement of an adenosine A1 agonist was also measured to examine in vitro sensitivity to caffeine as a function of age and neonatal caffeine exposure. Our studies demonstrated that the differential responses to adenosine receptor ligands seen as a function of both age and neonatal caffeine exposure could not be overcome by merely increasing the doses of ligand administered. In addition, the results of the binding studies indicated that changes in the adenosine receptor are occurring as a function of age in different regions of the brain of control animals and that this development is influenced by neonatal caffeine exposure.

Behavioral effects of exposure to caffeine during gestation, lactation or both

Open-field behavior and latencies of emergence from a darkened chamber to a brightly lit arena were recorded at 1, 2, 4 and 6 months after birth in male and female rats that had been exposed to 26 or 45 mg/kg/day caffeine ingested by dams in their drinking water during gestation, 25 or 35 mg/kg/day during lactation or to the two low or high doses ingested during both gestation and lactation. One or both of the gestational or lactational doses reduced locomotor activity and increased defecation in the open field at all ages for males only. Rearing was decreased for both sexes by 25 mg/kg/day lactational caffeine. Numbers of rats that failed to or took longer than 1 min to emerge into the brightly lit arena were increased by 26 mg/kg/day gestational caffeine. All rats that had been exposed to either dose combination of caffeine during both gestation and lactation showed less locomotor and rearing activity, reduced tendencies to emerge within 1 min and, at 6 months of age only, more defecation in the open field. It was concluded that the effects of gestational and lactational exposure to caffeine were additive in their modification of the developing brain as reflected in decreased motor activity possibly arising from heightened emotional reactivity to the testing situation. Hypersensitivity of males to caffeine exposure during either gestation or lactation separately seemed to diminish when exposure was increased for all rats through experience of the drug during both gestation and lactation. Possible involvement of caffeine-induced increases in adenosine receptors in the type of results obtained was discussed.