All of the following are compensatory mechanisms that have been proposed to explain the phenomena of tolerance to and withdrawal from drugs except down regulation of opiate receptors. The reinforcing aspect of opiate drugs involves receptors in the periaqueductal gray matter. It is involved in the intracellular processes involved in the development of withdrawal symptoms of opiates. It plays a role in regulating the activity of some genes. It binds with a second messenger.
Cocaine causes strong physical dependence.
Amphetamine causes dopamine transporters to run in reverse. It has considerable addictive potential. It stimulates acetylcholine receptors. It is self-administered in the form of tobacco, but not by animals. It causes dopamine release in the nucleus accumbens.