Cocaine and Amphetamines

Cocaine ('crack" in its concentrated form) and amphetamines ('speed"; "Ecstasy") increase the release of catecholamines, a broad group of chemical neurotransmitters in the brain. Dopamine is a catecholamine that gives rise to the subjective sensation of pleasure and promotes adventuresome, novelty-seeking behavior. Not surprisingly, cocaine and amphetamines produce euphoria, a sense of being on top of the world, plus high levels of energy.

My Amphetamine Study

I once took a single dose of amphetamine as a "normal" subject in a placebo-controlled study (I was assigned to amphetamine, as I discovered later). Before taking the amphetamine, I did fairly well on a neuropsychological task in which unusual shapes rapidly flashed on the computer screen. According to the rules, I had to tap an electronic button whenever I decided that the flashing shape on the display had previously been shown to me. Without my knowledge, the complexity of the shapes that were presented were automatically adjusted on-line to keep me at an 80 percent accuracy rate throughout the testing period. Later, I found out that although I scored well, the computer easily boxed me into the 80 percent zone for accuracy.

But after I took the amphetamine, things changed dramatically. My performance became flawless and the computer could not keep up; I was getting everything right even though the computer was throwing all it could at me to try to drop my performance from 100 percent to 80 percent accuracy. The investigator conducting the experiment later told me that she had to discard my data because my 100 percent accuracy rate eclipsed the 80 percent upper limit permitted in the experiment. So my results could not be combined with those from all the other subjects who had stayed within the 80 percent accuracy paradigm set by the computer.

My performance wasn't related to learning the test, because the shapes were truly nonsensical, even bizarre, and kept changing continuously on the computer screen. Rather, after a single dose of amphetamine, the manner in which I processed information changed dramatically. Even though the time interval between the flashing shapes was only a second or two, I felt as if I had all the time in the world to think about each shape, decide if I had seen it before (memory processing), and then respond by hitting the button if I had. The speed of processing of new information in my brain— which in this study involved registering the shape and checking it against my memory data bank of recently viewed shapes before making the decision to give the command to my fingers to tap (or not to tap) the elec tronic button—was now so fast that the test itself seemed to have become slow. In fact, later that same day I asked if the presentation of the nonsensical shapes had been slowed down for me, and I was told bluntly that this had not occurred.

This is a well-known effect of not only amphetamines but also cocaine. Messages are transmitted and processed much faster by nerve cells, probably because of increased dopamine neurotransmission. This effect of amphetamines has been used by students to cram for exams at the last minute.

Toxic Effects: Psychosis

With both drugs, excessive dopamine release can cause psychosis with hallucinations (hearing and seeing things that are not there) and delusions (false, bizarre beliefs). Amphetamine-induced psychosis symptoms are similar to paranoid schizophrenia, while cocaine-induced psychosis is typically associated with grandiosity and the hallucination of bugs crawling on the skin. The psychiatric symptoms are paramount, and memory loss is secondary.

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