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Caffeine has been shown to induce a transient hypertensive state in Wistar rats. The height to which the blood pressure rises in this caffeine-induced hypertension, and the duration of this hypertensive state was found to be dependent on the concentration of caffeine administered. Caffeine exposed to negatively ionized air was shown to undergo a loss in its pressor activity. This loss in pressor activity was found to be greater when the caffeine was exposed in solution than when it was exposed in the crystalline state. Once the blood pressures of Wistar rats were elevated with injections of caffeine and had again returned to normal levels there were no further rises in blood pressures with the administration of an equal number of injections of this drug. / Science, Faculty of / Botany, Department of / Zoology, Department of / Graduate

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The purpose of this study was to examine the effects of the relationship among caffeine consumption, levels of trait anxiety, and the personality factor of introversion/ extraversion on performance. In Phase I of this study, volunteers were screened for introversion/extraversi on using the Eysenck Personality Inventory (EPI) and fhigh/low trait anxiety using the State-Trait Anxiety Inventory (STAI). Based on the results of the two screening instruments the volunteers were categorized as high trait-anxious introverts (HTA/I), low trait-anxious introverts (LTA/I), high trait-anxious extraverts (HTA/E), or low trait-anxious extraverts (LTA/E). Using a table of random numbers, 30 subjects from each category were selected. These subjects were further randomly assigned to one of the two treatment levels of caffeine.In Phase II of this study each of the 120 subjects consumed either two milligrams of caffeine per kilogram of body weight or four milligrams of caffeine per kilogram of body weight in six ounces of Tang. After a 45-minute waiting period for the caffeine to enter the blood system, each subject completed the performance task, a seven-minute modified version of the Digit Symbol Scale (DSS) of the Wechsler Adult Intelliqence Scale (WAIS). The dependent variable was the total number of correct responses out of a possible score of 490.The hypotheses were tested using a Three-Way Analysis of Variance, and the F-test was applied to determine statistical significance. None of the three null hypotheses were rejected.

Seven men were studied during 30 minutes of leg ergometer cycling at approximately 70% V02 max to determine the effects of caffeine ingestion on the utilization of muscle glycogen. A caffeine solution (250 ml; 5 mg/kg body weight) given one hour prior to exercise (CAF trial), decreased the rate of muscle glycogen depletion by 36 + 11.86% (p. .005) as compared to a decaffeinated control trial. During the CAF treatment, there was a 16% increase in serum FFA prior to exercise. Exercise resulted in a removal of FFA from the blood in both trials. Muscle triglyceride levels prior to exercise in the CAF trial were nearly 23% higher than control levels and suggest, that excess FFA present prior to exercise in the CAF trial were esterified into triglyceride. Subsequent post-exercise values indicated a greater utilization of endogenous lipid. A model based on caffeine's stimulatory effects on muscle lipid mobilization and its inhibitory action on muscle phosphorylase a appears to be responsible for the lessened use of muscle glycogen.

The work in this dissertation aims to describe a simple new test for odor-recognition memory in rats that can be readily performed and results in an easily observable and lasting form of memory. This test has allowed for the demonstration of ethanol-induced retrograde memory impairments in rats when ethanol is administered during both the consolidation and reconsolidation phases of memory encoding. The observation that a high-dose of ethanol can cause retrograde memory impairments when administered immediately or within hours after learning has taken place is an original finding that may have implications for understanding human blackouts. Furthermore, the finding that ethanol can disrupt the reconsolidation of a previously consolidated memory has not been previously established. It is also demonstrated that caffeine can prevent ethanol’s memory impairing effects, a result that contributes a new piece of evidence for caffeine’s effects on the learning and memory process. This effect has been further investigated mechanistically and attributed to caffeine’s dual role as a phosphodiesterase type 5 inhibitor and adenosine A2A antagonist. Neither of these mechanisms alone appear to be sufficient enough to prevent the retrograde memory impairments seen with ethanol. It is hoped that this test and our findings will prove useful for future investigations into the effects of ethanol on learning and memory and the human phenomenon of alcohol-induced blackouts. / text

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