Behavioral and Side Effects of Caffeine

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Behavioral and Side Effects of Caffeine Caffeine is the most consumed psychoactive drug in the world (Solinas et al, 2002). Caffeine has been known to have many side effects on hour external behavior and our internal physiological behavior. We use caffeine in our lives to sometimes stay awake to study or just get through the day. Caffeine decreases the blood flow to the brain by constricting the blood vessels but can also increase blood flow after continuous intake that may cause headaches (Kalat, 2004). Caffeine has a tendency to block adenosine (A1-, A2A-, A2B-, A3), which increases throughout the day to allow us to sleep and then decreases as we sleep which allows us to wake. Thus, if caffeine blocks adenosine we are unable to sleep when feeling the urge or wanting to sleep, which may cause us to decrease our caffeine intake. Caffeine acts to antagonize adenosine receptors, which then affects cell populations because it counteracts many adenosine effects. The caffeine mainly has an effect on the A2a adenosine receptors which then elevates the energy metabolism in the brain and also causes a decrease in cerebral blood flow (Cameron,, 1990; Ghelardini,, 1997;,1992; Neuhauser-Berthold, 1997). Along with caffeine affecting the adenosine it also has an effect on GABA receptors and the release of dopamine (Nehlig, 1992). Caffeine not only blockades adenosine it also releases intracellular calcium, inhibits phosphodiesterases and blockade or regulatory sites of GABAa-receptors (Gupta and Gupta, 1999). Withdrawal symptoms of caffeine are headache, drowsiness, fatigue and lethargy (Gupta and Gupta, 1999). Dopamine and glutamate neurotransmission is modulated by adenosine in the striatum. Adenosine A1 in the nerve terminals inhibits dopamine and glutamate from being released. Caffeine has an effect in this system by antagonizing of adenosine, which can then stimulate neurotransmitters to release dopamine and stimulate dopamine receptors (Solinas et al, 2002). A study done on rats showed that caffeine increased extracelluar concentrations of dopamine and glutamate in the shell of the nucleus accumbens (Solinas et al, 2002). These results of dopamine and glutamate in the shell of the nucleus accumbens might be related to the psycho stimulant effects of caffeine (Solinas et al, 2002). Studies show that Dopamine2 receptors are needed for caffeine activation in the brain (Zahniseret al, 2000). Adenosine receptors, dopamine receptors and GABA have been shown in studies to be involved in

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