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02-02-2007, 03:03 AM
Cocaine
Cocaine acts by blocking the reuptake of certain neurotransmitters such as dopamine, norepinephrine, and serotonin. By binding to the transporters that normally remove the excess of these neurotransmitters from the synaptic gap, cocaine prevents them from being reabsorbed by the neurons that released them and thus increases their concentration in the synapses (see animation). As a result, the natural effect of dopamine on the post-synaptic neurons is amplified. The group of neurons thus modified produces the euphoria (from dopamine), feelings of confidence (from serotonin), and energy (from norepinephrine) typically experienced by people who take cocaine.
In addition, because the norepinephrine neurons in the locus coeruleus project their axons into all the main structures of the forebrain, the powerful overall effect of cocaine can be readily understood.
In chronic cocaine consumers, the brain comes to rely on this exogenous drug to maintain the high degree of pleasure associated with the artificially elevated dopamine levels in its reward circuits. The postsynaptic membrane can even adapt so much to these high dopamine levels that it actually manufactures new receptors. The resulting increased sensitivity produces depression and cravings if cocaine consumption ceases and dopamine levels return to normal.
Cocaine addiction (http://www.addictionsearch.com/treatment_articles/cocaine-addiction_13_1.html) is thus closely related to its effect on the neurons of the reward circuit.
Cocaine acts by blocking the reuptake of certain neurotransmitters such as dopamine, norepinephrine, and serotonin. By binding to the transporters that normally remove the excess of these neurotransmitters from the synaptic gap, cocaine prevents them from being reabsorbed by the neurons that released them and thus increases their concentration in the synapses (see animation). As a result, the natural effect of dopamine on the post-synaptic neurons is amplified. The group of neurons thus modified produces the euphoria (from dopamine), feelings of confidence (from serotonin), and energy (from norepinephrine) typically experienced by people who take cocaine.
In addition, because the norepinephrine neurons in the locus coeruleus project their axons into all the main structures of the forebrain, the powerful overall effect of cocaine can be readily understood.
In chronic cocaine consumers, the brain comes to rely on this exogenous drug to maintain the high degree of pleasure associated with the artificially elevated dopamine levels in its reward circuits. The postsynaptic membrane can even adapt so much to these high dopamine levels that it actually manufactures new receptors. The resulting increased sensitivity produces depression and cravings if cocaine consumption ceases and dopamine levels return to normal.
Cocaine addiction (http://www.addictionsearch.com/treatment_articles/cocaine-addiction_13_1.html) is thus closely related to its effect on the neurons of the reward circuit.