Funding for this site is provided by readers like you.
Pleasure and pain
Pleasure and Drugs
Avoiding Pain

Help Chimie et dépendance : un champ de recherche riche en débats Gene Therapy Restores Feeding Behavior to Starving Mice Pleasures of the brain
What is the role of dopamine in reward: hedonic impact, reward learning, or incentive salience? Dopamine Receptors: A Representative Family of Metabotropic Receptors Laboratoire de neuropharmacologie, Dr Louis-Éric TRUDEAU ERROR DETECTION IN THE GRAY MATTER : Have Scientists Discovered Intuition?
The Immorality of Morality : Morality and the Dopamine reward System Brain chemical shown to induce both desire and dread
Original modules
Your "Mental Stopwatch" Your "Mental Stopwatch"

There are five types of receptors for dopamine in the human brain, identified as D1 to D5. They are not all equally involved in pleasure-seeking behaviour. For instances, some studies have shown that D3 receptors appear to be more involved in the phenomenon of dependency. More recently, other studies have associated the activation of D1 receptors with the euphoriant effects of cocaine and the desire to obtain them.

Linked Module:  Neurons dopaminergiques Linked Module: Dopamine Action and Receptors Linked Module: Molecular Biology of the Dopamine Receptor Subtypes

Many hypotheses have been offered to try to identify the relationship between dopamine and pleasure. The first and simplest posited a direct causal connection between dopamine and the sensation of pleasure. In other words, it was thought that the increased dopamine level that accompanied a gratifying behaviour was the direct cause of its hedonic impact.


Model of a dopaminergic receptor with the associated G-protein


But doubts were cast on this theory by other experiments, in particular those showing that the increase in dopaminergic activity preceded the gratifying behaviour itself. A new hypothesis then arose, that dopamine acted as a facilitating factor in learning. According to this hypothesis, the amount of dopamine released by the brain prior to a behaviour is proportional to its potential for providing pleasure. Depending on whether the behaviour proves to be pleasant or unpleasant, the anticipatory dopamine level would be higher or lower the next time.

According to this same hypothesis, learning would enable this dopaminergic response to be transferred from an unconditioned stimulus (such as an open can of tuna, for your cat) to a conditioned one (the noise of the can opener). This hypothesis accords dopamine a central role in the way we learn to remember sources of gratification.

Still other studies, however, have raised questions about this role of dopamine as a modulator of learning. In particular, certain rat experiments showed that even if the animals kept pressing the lever by which they stimulated their own brains, the actual level of dopamine in their brains kept decreasing.

From these studies, a new hypothesis emerged that associated dopamine more with novelty and its ability to increase the animals’ motivation to approach the gratifying object. This “incentive value” would be a distinct component of what we commonly call “pleasure seeking.” In other words, the dopaminergic system would be necessary for wanting the gratifying object, but not for liking it or for learning to remember new sources of pleasure.

  Presentations | Credits | Contact | Copyleft