Dissociative antagonistic effects of caffeine on alcohol-induced impairment of behavioral control.

The present study examined the separate and combined effects of alcohol and caffeine on behavioral control in a context in which preliminary cues signaled the likelihood that a response should be executed or inhibited. Social drinkers (N = 12) performed a cued go/no-go task that measured control as the quick execution of responses to go targets and sudden suppression of responses to no-go targets. Performance was tested under 3 doses of caffeine (0.0 mg/kg, 2.0 mg/kg, and 4.0 mgl/g) in combination with 2 doses of alcohol (0.0 g/kg and 0.65 g/kg). Alcohol impaired both inhibitory and activational aspects of behavioral control. Caffeine antagonized alcohol effects on response execution but had no effect on inhibitory control. The findings highlight potential differences in how activational and inhibitory aspects of behavioral control respond to drug interactions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Clubgoers and their trendy cocktails: Implications of mixing caffeine into alcohol on information processing and subjective reports of intoxication.

Alcoholic drink preferences in college students have made an interesting shift recently, with trends in consumption leaning toward caffeinated alcohol in various forms (e.g., Red Bull and vodka or caffeinated beers such as Anheuser-Busch's B-to-the-E). Despite the dramatic rise in popularity of these beverages, little research has examined the combined effects of alcohol and caffeine, which is problematic for adequately informing the public about the risk or lack thereof of these drinks. The purpose of this study was to directly investigate the acute effects of alcohol and caffeine, alone and in combination, on well-validated measures of cognitive performance and subjective intoxication in social drinkers. Participants (N = 12) performed a psychological refractory period task that measured dual-task interference as the prolonged reaction time to complete the 2nd of 2 tasks performed in close temporal sequence. Performance was tested under 2 active doses and 1 placebo dose of caffeine (0.0 mg/kg, 2.0 mg/kg, and 4.0 mg/kg) in combination with 1 active dose and 1 placebo dose of alcohol (0.0 g/kg and 0.65 g/kg). As expected, alcohol impaired task performance by increasing dual-task interference and increasing errors. The coadministration of caffeine counteracted the effects of alcohol on interference but had no effect on the degree to which alcohol increased errors. Subjective measures of intoxication showed that coadministration of caffeine with alcohol reduced participants' perceptions of alcohol intoxication compared with administration of alcohol alone. The results highlight the complexity of drug interactions between alcohol and caffeine. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behavioral effects of combining alcohol and caffeine: Contribution of drug-related expectancies.

This experiment tested the hypothesis that drinkers' expectations about the behavioral effect of combining alcohol and caffeine predicted their psychomotor performance when they expected to receive both drugs. Fifty male social drinkers were assigned to 1 of 4 treatment groups or to a no-treatment control group. Participants in the 4 treatment groups expected and received alcohol (0.56 g/kg). The expectation and the receipt of caffeine (4.4 mg/kg) were manipulated independently. After training on a Pursuit Rotor task, participants rated the expected effect of combining alcohol and caffeine and then received the drug treatments. As predicted, individual differences in expected effects predicted participants' performance when they expected to receive caffeine in combination with alcohol. Regardless of whether caffeine was actually received, those who expected the most impairment from the drug combination performed most poorly. This evidence has implications for understanding factors that contribute to individual differences in behavioral responses to drugs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Psychomotor performance under alcohol and under caffeine: Expectancy and pharmacological effects.

Tested the hypothesis that Ss' expectancies about drug effects on psychomotor performance would predict their responses to drug and placebo. 40 male undergraduates were assigned to 1 of 5 treatments: alcohol (0.56 g/kg), placebo alcohol, caffeine (2.93 mg/kg), placebo caffeine, or no treatment. Groups received preliminary training on a pursuit rotor task before rating the effect that caffeine or alcohol was expected to have on their performance. Ss' performance was measured under the treatments and showed impairment under alcohol and improvement under caffeine. However, regardless of whether they received a drug or placebo, those who expected the most impairment performed the most poorly. Results indicate the importance of expectancies in understanding individual differences in response to drugs and placebos. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Column-switching high-performance liquid chromatographic assay for determination of apigenin and acacetin in human urine with ultraviolet absorbance detection

Postweaning social isolation can influence the sensitivity of rats to several effects of drugs of abuse. The present study investigated the influence of postweaning housing conditions on the sensitivity of rats to the aversive effects of a number of psychoactive agents using a conditioned taste aversion (CTA) test procedure. Development of a CTA was assessed by pairing administration of the drug with the consumption of a 0.05% (weight/volume) saccharin solution in water-deprived (18 h) rats in a 20 min drinking period. Saccharin consumption was then measured in 20 min test sessions over the next 4 consecutive days. Consumption of saccharin solution was significantly reduced in both isolated and enriched rats following administration of d-amphetamine (2 mg/kg), cocaine (30 mg/kg), morphine (10 mg/kg), nicotine (1.0 mg/kg), caffeine (20 mg/kg), alcohol (1.5 g/kg), and LiCl (0.15 M, 4 ml/kg). There was no significant effect of housing conditions on the CTA induced by cocaine, nicotine, alcohol, or LiCl; however, isolation-reared rats were found to be less sensitive to the aversive effects of d-amphetamine, morphine, and caffeine in this paradigm. These results suggest that rearing rats in social isolation induces an attenuation in sensitivity to the aversive effects of some psychoactive agents.     

Alcohol-Induced Impairment of Inhibitory Mechanisms Involved in Visual Search.

The present study examined the effects of alcohol on the ability to perform a cued target detection task that measured inhibition of return (IOR). IOR is a reflexive inhibitory mechanism that delays attention from returning to a previously attended location and has been shown to increase the efficiency of a visual search. Ten social drinkers performed the task under 3 alcohol doses: 0.0 g/kg (placebo), 0.45 g/kg, and 0.65 g/kg. The results showed both active alcohol doses reduced the IOR effect by shortening its duration of influence. The reduced duration of IOR under alcohol suggests that repeated searches in previously explored locations might be more likely under the drug, thereby reducing search efficiency. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preresponse cues reduce the impairing effects of alcohol on the execution and suppression of responses.

The present study examined the effects of alcohol on the ability to execute and inhibit behavior in a context in which preliminary information signaled the likelihood that a response should be executed or suppressed. Social drinkers (N =12) performed a cued go/no-go task that required quick responses to go targets and suppression of responses to no-go targets. Performance was tested under 3 doses of alcohol: 0.65 g/kg, 0.45 g/kg, and 0.0 g/kg (placebo). Alcohol had no effect on inhibition and execution when cues correctly signaled these actions. By contrast, alcohol impaired inhibition and execution in a dose-dependent manner when cues incorrectly signaled actions. These findings are consistent with a resource limitation account of alcohol impairment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Processing bimodal stimulus information under alcohol: Is there a risk to being redundant?

The impairing effects of alcohol are especially pronounced in environments that involve dividing attention across two or more stimuli. However, studies in cognitive psychology have identified circumstances in which the presentation of multiple stimuli can actually facilitate performance. The “redundant signal effect” (RSE) refers to the observation that individuals respond more quickly when information is presented as redundant, bimodal stimuli (e.g., aurally and visually), rather than as a single stimulus presented to either modality alone. The present study tested the hypothesis that the response facilitation attributed to RSE could reduce the degree to which alcohol slows information processing. Two experiments are reported. Experiment 1 demonstrated the validity of a reaction time model of RSE by showing that adults (N = 15) responded more quickly to redundant, bimodal stimuli (visual + aural) versus either stimuli presented individually. Experiment 2 used the RSE model to test the reaction time performance of 20 adults following three alcohol doses (0.0 g/kg, 0.45 g/kg, and 0.65 g/kg). Results showed that alcohol slowed reaction time in a general dose-dependent manner in all three stimulus conditions with the reaction time (RT) speed-advantage of the redundant signal being maintained, even under the highest dose of alcohol. Evidence for an RT advantage to bimodal stimuli under alcohol challenges the general assumption that alcohol impairment is intensified in multistimulus environments. The current study provides a useful model to investigate how drug effects on behavior might be altered in contexts that involve redundant response signals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Driver training conditions affect sensitivity to the impairing effects of alcohol on a simulated driving test to the impairing effects of alcohol on a simulated driving test.

[Correction Notice: An erratum for this article was reported in Vol 16(2) of Experimental and Clinical Psychopharmacology (see record 2008-03846-009). The correct title of the article should read "Driver training conditions affect sensitivity to the impairing effects of alcohol on a simulated driving test".] Research shows that prior behavioral training in a challenging environment reduces alcohol-induced impairment on simple psychomotor tasks. However, no studies have examined if this relationship generalizes to driving performance. The present study examined simulated driving performance and tested the hypothesis that a challenging training history would protect against the impairing effects of alcohol on driving performance. The challenging training history involved driving in a visually-impoverished environment. Thirty adults were randomly assigned to one of three groups. Two groups were tested under alcohol (0.65 g/kg) after prior experience performing the task under either a visually-impoverished environment or a normal visual environment. The remaining group served as a control and was trained and tested under the visually-impoverished condition environment. Results showed that individuals trained in the impoverished environment displayed sober levels of performance when their performance was subsequently tested under alcohol. By contrast, volunteers trained in a normal environment showed impairment under alcohol. The findings suggest that differences in driving training history can affect a driver's sensitivity to the impairing effects of alcohol. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behavioral tolerance and sensitization to alcohol in humans: The contribution of learning.

This experiment tested the hypothesis that tolerance or sensitization to repeated alcohol doses is predicted by the particular response (diminished or augmented impairment) that is reinforced under drug. Twelve male social drinkers were assigned to a tolerance (T) or sensitization (S) group (n?=?6) and performed a psychomotor task under 0.62 g/kg of alcohol on 5 separate sessions. The 1st session preceded training and determined that the groups' drugged performance did not differ. On 3 subsequent sessions verbal feedback reinforced diminished impairment in Group T and augmented impairment in Group S. During these sessions, Groups T and S displayed tolerance and sensitization, respectively. The final session showed that training effects were retained without reinforcement. The results extend the evidence on the effect of reinforcement to show that it can enhance sensitization as well as tolerance. The findings demonstrate that behavioral variables modulate the response to alcohol and imply that tolerance and sensitization may be affected by a common learning process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Increased sensitivity to the disinhibiting effects of alcohol in adults with ADHD.

The acute impairing effects of alcohol on inhibitory control have been well documented in healthy drinkers. By contrast, little is known about alcohol effects in individuals with disorders characterized by poor impulse control, such as those with attention-deficit/hyperactivity disorder (ADHD). Alcohol could produce greater inhibitory impairment in these individuals. The present study tested this hypothesis in adults with ADHD (n = 10) and controls (n = 12) using the cued go/no-go task. The task requires quick responses to go targets and suppression of responses to no-go targets following the presentation of cues. Prior research on healthy adults has shown that valid cues can protect against alcohol impairment (Marczinski & Fillmore, 2003). Performance was tested under 3 doses of alcohol: 0.65 g/kg, 0.45 g/kg, and 0.0 g/kg (placebo). Alcohol dose-dependently increased inhibitory failures in controls in the invalid, but not the valid, cue condition. By contrast, those with ADHD displayed significant alcohol impairment regardless of cue condition. Thus, unlike controls, valid cues offered little protection from the disinhibiting effects of alcohol in drinkers with ADHD, suggesting an increased sensitivity to alcohol impairment of inhibitory control. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Alcohol Increases Reliance on Cues That Signal Acts of Control.

This study examined the effects of alcohol on the ability to execute and inhibit behavior in a context in which preliminary information signaled the likelihood that a response should be executed or suppressed. Adults (N = 24) performed a cued go/no-go task that required quick responses to go targets and suppression of responses to no-go targets. Cue dependency was manipulated by varying the predictive validity of the cues, and performance was tested under 3 doses of alcohol: 0.00 g/kg, 0.45 g/kg, and 0.65 g/kg. Dose-dependent increases in cue dependence were only observed with highly predictive cues. Results suggest that alcohol-induced increases in stimulus control over behavior might be most likely in situations when stimulus control over behavior has already been established. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Alcohol, Intentional Control, and Inappropriate Behavior: Regulation by Caffeine or an Incentive.

This study shows that reduced intentional control under alcohol can be counteracted by caffeine or an environmental incentive. Four groups of social drinkers (n = 11) received 1 of the following: 0.62 g/kg alcohol (A), alcohol with 4.4 mg/kg caffeine (AC), alcohol with a rewarding monetary incentive (AR), or a placebo (P). They then performed a word stem completion task that provided separate measures of the influence of controlled and automatic processes governing responses. Controlled processes were depressed in Group A compared with Group P, whereas Groups AR and AC did not differ from Group P. Most inappropriate responses were displayed under alcohol alone, fewer with caffeine, and least with incentive. No treatment significantly affected automatic processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An alcohol model of impaired inhibitory control and its treatment in humans.

This study developed a model of impaired inhibitory control in humans to test the efficacy of treatments for this deficit. Male social drinkers (N?=?35) practiced a "go–stop" task that measured response inhibition. They then were assigned to 1 of 5 groups (n?=?7) that performed the task under a different treatment. The model of impaired inhibitory control was provided by administering 0.62 g/kg alcohol to 1 group (A), whose response inhibition was compared with a placebo group (P). The other 3 groups received 0.62 g/kg alcohol plus a treatment designed to ameliorate alcohol impairment of inhibitory control: behavioral reinforcement (B), or 4.4 mg/kg caffeine (C), or a combination of both (B?+?C). Alcohol impaired inhibitory control, and all 3 treatments (B, C, and B?+?C) counteracted the impairment. The findings indicate that alcohol impairment of response inhibition may provide a useful human model to test conditions that may ameliorate or exacerbate deficits in behavioral control induced by drugs or other factors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contraints on information processing under alcohol in the context of response execution and response suppression.

This study tested the degree that alcohol restricts information processing on tasks requiring response execution and response suppression. A dual task required 12 participants to respond to 2 task stimuli (Tasks 1 and 2) presented in close succession. The task was performed before and after receiving 3 alcohol doses (placebo, 0.45 g/kg, and 0.65 g/kg) administered on separate days in a counterbalanced order. Alcohol increased task interference, as evidenced by increased time to respond to Task 2. Impairment was comparable regardless of whether Task 1 required a response to be executed or suppressed. The evidence supports a resource limitation account that argues that alcohol reduces capacity to process information required for execution and suppression of responses. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acute alcohol tolerance on subjective intoxication and simulated driving performance in binge drinkers.

High rates of binge drinking and alcohol-related problems, including drinking and driving, occur among college students. Underlying reasons for the heightened impaired driving rates in this demographic group are not known. The authors hypothesized that acute tolerance to the interoceptive cues of intoxication may contribute to these maladaptive decisions to drive in binge drinkers. Groups of binge-drinking and non-binge-drinking college students (N = 28) attended sessions during which they received a moderate dose of alcohol (0.65 g/kg) or a placebo. The development of acute tolerance to subjective ratings of intoxication and simulated driving performance was assessed by comparing measures taken during the ascending phase and descending phases of the blood alcohol curve. Compared with placebo, alcohol increased ratings of intoxication and impaired multiple aspects of simulated driving performance in both binge and non-binge drinkers. During the descending phase of the blood alcohol curve, binge drinkers showed acute tolerance to alcohol’s effect on subjective intoxication, and this effect was accompanied by an increased rating of willingness to drive. By contrast, non-binge drinkers showed no acute tolerance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of ethanol and caffeine on behavior in C57BL/6 mice in the plus-maze discriminative avoidance task.

Introduction: Caffeine is frequently consumed concurrent to or immediately following ethanol consumption. Identifying how caffeine and ethanol interact to modulate behavior is essential to understanding the co-use of these drugs. The plus-maze discriminative avoidance task (PMDAT) allows within-subject measurement of learning, anxiety, and locomotion. Methods: For training, each mouse was placed in the center of the plus-maze for 5 min, and each time that the mouse entered the aversive enclosed arm, a light and white noise were turned on. At testing, each mouse was returned to the center of the maze for 3 min. No cues were turned on during testing. Results: Ethanol (1.0–1.4 g/kg) dose-dependently decreased anxiety and learning, and increased locomotion. Caffeine (5.0–40.0 mg/kg) dose-dependently increased anxiety and decreased locomotion and learning. Caffeine failed to reverse ethanol-induced learning deficits. However, 1.4 g/kg ethanol blocked the anxiogenic effect of caffeine. Discussion: Although caffeine and ethanol interact to modulate behavior in the PMDAT, caffeine does not reverse ethanol-induced learning deficits. Ethanol-induced anxiolysis may contribute to alcohol consumption, while ethanol’s blockade of caffeine-induced anxiogenesis may contribute to co-use. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Correction to Harrison et al. (2007).

Reports an error in "Driver training conditions affect sensitivity to the impairing effects of alcohol on a simulated driving test to the impairing effects of alcohol on a simulated driving test" by Emily L. R. Harrison, Cecile A. Marczinski and Mark T. Fillmore (Experimental and Clinical Psychopharmacology, 2007[Dec], Vol 15[6], 588-598). The correct title of the article should read "Driver training conditions affect sensitivity to the impairing effects of alcohol on a simulated driving test". (The following abstract of the original article appeared in record 2007-18976-010.) Research shows that prior behavioral training in a challenging environment reduces alcohol-induced impairment on simple psychomotor tasks. However, no studies have examined if this relationship generalizes to driving performance. The present study examined simulated driving performance and tested the hypothesis that a challenging training history would protect against the impairing effects of alcohol on driving performance. The challenging training history involved driving in a visually-impoverished environment. Thirty adults were randomly assigned to one of three groups. Two groups were tested under alcohol (0.65 g/kg) after prior experience performing the task under either a visually-impoverished environment or a normal visual environment. The remaining group served as a control and was trained and tested under the visually-impoverished condition environment. Results showed that individuals trained in the impoverished environment displayed sober levels of performance when their performance was subsequently tested under alcohol. By contrast, volunteers trained in a normal environment showed impairment under alcohol. The findings suggest that differences in driving training history can affect a driver's sensitivity to the impairing effects of alcohol. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prostate cancer

In previous research, we found an independent interaction of alprazolam and caffeine in rats under acute dose regimens using two measures (reinforcement rate and shorter-response rate) of a differential reinforcement of low rate performance (DRL 45-s) in 3-h sessions. Applying the same behavioral endpoints, the present study investigated the alprazolam-caffeine interaction under chronic dose regimens. Both drugs were administered by the oral route. Acute alprazolam and caffeine dose-response curves (DRCs) were characterized and were then used to determine the maintenance dose for the respective chronic dose regimens. Both drugs decreased the reinforcement rate and increased the shorter-response rate in a dose-related fashion. An alprazolam DRC also was determined during chronic-caffeine, chronic-alprazolam, and concurrent chronic-caffeine-alprazolam dose regimens. Complete tolerance to caffeine-induced rate changes was observed on the second day. Incomplete tolerance occurred only at higher alprazolam doses (7-12.5 mg/kg). Cross tolerance was not found between alprazolam and caffeine. Upon discontinuation of both drugs, performance progressively returned to baseline. The four alprazolam DRCs as well as the effect-time profiles demonstrated that caffeine altered neither the magnitudes nor the patterns of alprazolam effects on the two rates under chronic dose regimens. The P?ch DRC method further confirmed the independent interaction of alprazolam and caffeine. Thus, the independence of the interaction held for both the acute and chronic dose regimens despite the development of tolerance in the latter regimens.     

Subjective responses to nicotine in smokers may be associated with responses to caffeine and to alcohol.

Sensitivity in responses to one drug may relate to sensitivity to other drugs, suggesting broad individual differences in characteristic responsivity across drugs. Data from two separate studies of smokers were reanalyzed to examine associations between acute subjective and cardiovascular effects of nicotine vs. caffeine and between nicotine vs. alcohol. Typical intakes of cigarettes, alcohol, and caffeine were included as covariates when they were correlated with the responses of interest. Significant associations between nicotine and caffeine were seen for most of the subjective measures and for blood pressure responses. Fewer significant associations were observed between nicotine and alcohol. Responses associated between nicotine and both of the other drugs tended to reflect psychomotor stimulation. These results suggest that smokers who are more responsive to some of nicotine's subjective and blood pressure effects are also more sensitive to the same effects of caffeine and, to a lesser extent, of alcohol. (PsycINFO Database Record (c) 2010 APA, all rights reserved)