These activations are in line with the known effects of caffeine on vigilance. Indeed, the pattern of consumption of caffeine throughout the day shows that caffeine is mostly consumed to increase the level of vigilance,35 and caffeine is well known to impair sleep.3,38 Likewise, caffeine focuses available attention and energy on the task to complete, mostly by
limiting distracting external stimuli.39 Finally, the anterior insular cortex, which was activated by caffeine, regulates cardiovascular function and respiratory rhythms. Numerous epidemiologic studies have focused on the effects Inhibitors,research,lifescience,medical of coffee and caffeine on cardiovascular risk, cholesterol, and blood pressure (for review see ref 40). The data currently available indicate that a moderate caffeine intake does not adversely affect cardiovascular function. However, Inhibitors,research,lifescience,medical a recent meta-analysis on the relationship between coffee, caffeine, and blood pressure reported that caffeine consumption increases blood pressure by a mean value of 4.2 mm for systolic and 2.0 mm
Hg for diastolic blood pressure.41 In the present study, the values of systolic blood pressure slightly increased after caffeine, especially in the HC group, but because of the large PS-341 nmr interindividual variability, this slight change was not significant. In the present study, the main difference in caffeine-induced brain activation between LC and HC subjects Inhibitors,research,lifescience,medical was the involvement of hypothalamus which was the single region affected in HC, while perfusion was not affected in hypothalamus when the same amount of Inhibitors,research,lifescience,medical caffeine was given to LC. When both groups were pooled, the caffeine-induced brain activation
was significant in all areas involved in the two groups. In the present study, we did not record any brain activation or inhibition in the different components of the brain circuit of dependence. In the presurgical followup of a 20-year-old male epileptic patient with right temporal lobe epilepsy and seizures Inhibitors,research,lifescience,medical induced by compulsive smoking, we were incidentally able to show that nicotine induced clear focal brain activation almost in the nucleus accumbens, the key area involved in addiction and reward, while caffeine (3.5 mg/kg) did not induce change in brain activation in the nucleus accumbens (Marescaux, Namer, and Nehlig, unpublished data). Therefore, these earlier data plus the present data reflect that caffeine at doses representing about two cups of coffee in one sitting does not activate the circuit of dependence and reward and especially not the main target area, the nucleus accumbens.10-12 This lack of effect is present both in light and heavy coffee drinkers who had claimed that they felt “dependent” on coffee. This data is in agreement with our previous data on rats in which the doses of 2.5 and 5.0 mg/kg also failed to activate the circuit of dependence and reward.