Caffeine's Effects on Performance and Mood are Independent of Age and Gender.

The purpose of this study was to determine if there were age or gender specific effects of caffeine, as measured by cognitive tasks and mood assessments known to be sensitive to caffeine. The subjects were healthy, non-smoking volunteers between the ages of 18 and 30 (6 male and 6 female), and over the age of 60 (6 male and 6 female). Only low and moderate consumers of caffeine (daily intake < 400 mg) were enrolled in the double-blind, placebo controlled, crossover design. The order of caffeine dosing (placebo, 64, 128, and 256 mg) was counterbalanced by use of a complex Latin Square sequence of administration. Analysis of the data from all measures indicated that the effects of caffeine were no different in either males or females, or in the young or elderly volunteers. A significant dose-dependent improvement in performance of all subjects was observed in a modified version of the Wilkinson Auditory Vigilance Test. Additionally, significant dose-dependent improvements in mood state were observed in all subjects as assessed by the Profile of Mood States, Multiple Affect Adjective Check List, and The Caffeine Analog Scales. The results of this study suggest that the performance and mood enhancing effects of caffeine are neither age nor gender specific.

Naltrindole, a delta-opioid antagonist, blocks MDMA's ability to enhance pressing for rewarding brain stimulation.

Twelve rats were each fixed with a chronically indwelling bipolar electrode for stimulation of the medial forebrain bundle as it courses through the hypothalamus. These rats were trained to press a bar for intracranial stimulation of 0.3-s trains of 60 Hz sine waves for 10 min daily at three intensities. One intensity was just above threshold for maintaining pressing, one intensity was a high intensity that sustained considerable pressing, but not maximum pressing, and the other was intermediate to the others. After stable rates of pressing were obtained, rats received MDMA daily. MDMA significantly increased rates of pressing. Prior to a day when rats received MDMA, they also received an injection of naltrindole, a selective delta-opioid receptor antagonist. Naltrindole blocked MDMA's enhancement of pressing for reinforcing brain stimulation.

alpha(2)-Adrenoceptor antagonists and propensity to take alcoholic beverages.

Rats were maintained on a daily regimen involving a 2h opportunity to take both water and a sweetened alcoholic beverage (12% ethanol, 0.25% saccharin). After 3 weeks on this regimen, rats regularly take substantial amounts of alcohol. After stabilization, injections of alpha(2)-adrenergic antagonists were administered, 15min before the opportunity to drink. Yohimbine and methoxyidazoxan dose relatedly decreased intake of alcoholic beverage and increased intake of water. In Experiment 2, a number of rats were taken off the daily regimen for 9 days, then returned to it. Across the first 12 days of the reinstated daily regimen, half the rats received placebo and half methoxyidazoxan. The group receiving placebo rapidly returned to taking large amounts of alcoholic beverage while the group receiving methoxyidazoxan did not. In Experiment 3, it was shown that a dose of methoxyidazoxan that decreased intakes of alcoholic beverage did not decrease intakes of other palatable beverages. In Experiment 4, it was shown that yohimbine persistently reduced intakes of alcoholic beverage with daily administration. These results indicate that alpha(2)-antagonists might be effective pharmaceutical adjuncts to other treatments for alcohol abuse and alcoholism.