"Many paths of pleasure in the brain employ dopamine messengers [neurotransmitters] in their reinforcement. When we find ourselves partial to some experience, it is the dopamine system that reinforces the feeling and determines that we will seek it again. Many addictive drugs, likewise, alter dopamine in the brain and stimulate this reward system, sometimes producing manic-like behavior. The "buzz" described by those taking amphetamines (speed), or the "rush" of snorting cocaine, is the subjective "high" of the sudden increase of brain dopamine activity that these drugs stimulate."
"Cocaine is one of the most powerful dopamine-enhancing drugs. It achieves its effect at the synapse by blocking the transporter of the neuron's recycling system for dopamine, thus dramatically increasing the amount of dopamine available to stimulate neurotransmission. Through this mechanism, cocaine precipitates a transient state of hypomania—with euphoria, sleeplessness, and increased energy—in virtually all who take it. Furthermore, in individuals of bipolar temperament it will commonly precipitate a sustained manic episode ... In contrast to many other drugs of addiction, where tolerance occurs, the craving for cocaine increases with chronic use, making it one of the most dangerous of the addictions."
"Natural opioid [from opium] peptides are released as messengers in the brain under stressful conditions and physical injury. Appropriately named endorphins (meaning "internal morphine"), these "internal pain pills" help explain opiate addiction. Morphine and heoin, drugs of the opiate family, have a very high affinity for the brain receptors through which the endorphins operate."
Peter C. Whybrow, "A Mood Apart."
Don't. Experimenting with drugs is for the professionals.