![]() This is thought to be one of the major mechanisms by which the xanthines exert their stimulant effects, but there are almost certainly more. This means they "block" the adenosine receptors, which tend to be located in the brain regions involved in regulating sleep and wakefulness, such as the tuberomammilarry nucleus of the hypothalamus. ![]() They have number of different physiological effects on the body, perhaps most importantly adenosine receptor antagonism. However, some of the important ones in coffee that are known to be psychoactive are:Ĭaffeine, Theobromine, and Theophylline - All three of these are xanthines, a class of chemical compounds similar to purines, the nitrogenous bases that include adenine and guanaine. Plants are generally loaded with a number of different chemicals, so it can be hard to isolate just a few. Reacquisition of tolerance tends to be more rapid than first tolerance at least in part because of a well known finding in the extinction literature called rapid reacquisition. In contrast, switching from regular to decaf would still impact pharmacodynamic tolerance, but would also have an effect on behavioral tolerance due to extinction of at least some of the conditioned stimuli acquired while drinking caffeinated coffee. For example, simply not drinking coffee for 21 days will affect pharmacodynamic tolerance to a great extent but behavioral tolerance to little or no extent. Withdrawal side-effects are not equally caused by all 3 tolerances. The 3 tolerance are acquired at different rates and abate at different rates (and to different extents). conditioned compensatory responses & other effects related to Pavlovian and operant conditioning). changes in receptor densities & sensitivities, compensation of other NT, NM systems, etc. Three kinds of tolerance are generally recognized: pharmacokinetic (metabolic tolerance, factors affecting the distribution and elimination of the drug through and from the body's tissues), pharmacodynamic (cellular changes, e.g. We make our world significant by the courage of our questions and by the depth of our answers.
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