The Darker Side of Pleasure

The Darker Side of Pleasure

The cargo is the famous molecule dopamine. The nucleus accumbens uses dopamine to mediate its electrical signaling to the VTA. Dopamine is a neurotransmitter. In fact, it's one of the excitatory neurotransmitters – that is, its function stimulates nerve cells into action (as opposed to inhibiting them).

Dopamine follows the normal course of any neurotransmitter. The presynaptic cell releases dopamine into the synaptic cleft. The dopamine travels across the clef to the neighboring postsynaptic cell, where it binds to a receptor, stimulating it into action. The dopamine is released. It ends up back in its neural origin in a process known as reuptake.

Dopamine is involved in a bewildering number of behaviors. The neurotransmitter is involved in learning and memory formation. It's also involved in emotional arousal, and feeling pain and motor activity.

Its deregulation can have severe consequences. If you make too much of it, you may get schizophrenia. This idea is known as the dopamine hypothesis of schizophrenia. On the other hand, dopamine deficiencies in specific areas of the brain cause Parkinson's disease. In addition to its function of mediating pleasure, it's also involved in the ability to coordinate muscle movement.

One of its most insidious functions is the role it plays in addictive behaviour – and how powerfully we can be drawn to pleasure when overstimulated. This toxic effect can be illustrated by one of the most heart-breakingly familiar experiments in all of brain science. It was first designed in the lab of James Olds.

The basic design of the experiments is as follows. Tiny metal electrodes were inserted into the nucleus accumbens of a lab rat, allowing the region to be stimulated electrically. The electrode apparatus was connected to a bar in the cage. Every time the animal pressed the bar, electricity flowed through the electrode, stimulating the nucleus accumbens. Because the region mediates pleasure, every time the rat pressed the lever, the animal experienced pleasure.

Text to the brain is simply a complicated picture. Illustration by Elena.

This landmark study provided many great insights into the addictive side of pleasure. The nucleus accumbens electrically stimulates the VTA via dopamine, the molecular cargo. As a result, you feel pleasure. If you stimulate it too much, really bad things can happen. Chief amongst these is the experience of addiction.

Put simply, addiction is the state of behavioral dependence on a chemical substance or activity. Some behaviors, such as an addiction to gambling, show the same hallmarks of addictive behavior.

They even involve some of the same neurological processes as chemical addictions. The following are the tree main hallmarks of addictive behavior:

1. Craving: The most obvious characteristic of addiction is an intense craving for a substance often after casual use. In the case of crack cocaine, the high comes very quickly, a high so pleasurable that most people want more of the drug as soon as the high subsides, which is soon, because the high only lasts a few minutes. Cravings set in within the first hour after ingestion. As the days and weeks go by, you consume more of it in an attempt to repeat the initial buzz.
2. Tolerance : Tolerance is defined as a reduction over time of the ability of a drug's “regular“ dosage to get you high. After a while, you have to take more of the drug to get a buzz. The high becomes less and less intense, so you begin consuming more of the drug, attempting to reestablish the pleasure. Eventually, the drug no longer gets you high. You have to take it just to feel normal, just to function, and to avoid the third characteristic of addictive behavior: withdrawal.
3. Withdrawal symptoms. The drug's most insidious characteristic comes from the fact that, over time, your body switches from pleasure seeking to aversion avoidance. You begin to experience withdrawal if you can't ingest the drug. Now you're not looking to the drug for a buzz; you're looking to the drug for survival. In the case of cocaine, you can become depressed (even suicidal), fatigued, hostile, anxious, paranoid, violent, homicidal, and equipped with such a craving to get more of the stuff that nothing else in life seems to matter. And when/if you finally do get more stuff, you have to take such large dosages that it can become life threatening.

Researchers have discovered, in broad outlines, the biology behind the addictive behaviors that are seen in substance abuse issues. We know the following four things:

1. We know that the VTA is deeply involved in the initial phases of setting up cocaine addiction.
2. We know that the nucleus accumbens, which the VTA targets, helps mediate the pleasure responses to the drugs.
3. We know that both regions, and the neural circuits that connect them traffic in dopamine.
4. We know that drug abuse overdrives these systems, releasing massive quantities of dopamine into their circuitry. The buzz is so powerful that you only want to get high.

The darker side of the pleasure. One of the most insidious functions of dopamine is the role it plays in addictive behavior. Photo by Elena.