The brain consists of multiple nerve cells that transfer information, through chemical messages. Cocaine blocks the dopamine transporter, which is the 'feel good' messenger. When the dopamine transporter becomes blocked the brain generates an overload of this sensational messenger and we naturally want more; become addicted. How cocaine works is explained in this BBC preview. Scientists have discovered regions within the brain that, when stimulated, produce feelings of pleasure. One neural system that appears to be most affected by cocaine originates in a region, located deep within the brain, called the ventral tegmental area shortly called as VTA. Nerve cells originating in the VTA extend to the region of the brain known as the nucleus accumbens, one of the brain's key pleasure centers. In studies using animals, for example, all types of pleasurable stimuli, such as food, water, sex, and many drugs of abuse, cause increased activity in the nucleus accumbens. Drugs of abuse are able to interfere with this normal communication process. For example, scientists have discovered that cocaine blocks the removal of dopamine from the synapse, resulting in an accumulation of dopamine. This buildup of dopamine causes continuous stimulation of receiving neurons, probably resulting in the euphoria commonly reported by cocaine abusers. As cocaine abuse continues, tolerance often develops. This means that higher doses and more frequent use of cocaine are required for the brain to register the same level of pleasure experienced during initial use.