Pleasure and the reward circuit: neurobiological aspects

In the brain, certain regions are responsible for rewarding the performance of vital functions (eating, drinking, reproduction...) with the appearance of a sensation of pleasure. This is known as the reward circuit. Within the brain, information circulates in the form of nerve impulses (electrical activity). To pass from neuron to neuron, the nerve impulse is transformed into a chemical message: the neuron secretes substances called neurotransmitters (dopamine, serotonin...) which cross the synapse (contact space between two neurons). These neurotransmitters have specific structures and functions. Once released into the synapse, the neurotransmitter binds to a specific receptor (dopaminergic, serotonergic, etc.) on the neuron receiving the message. This "recapture" removes the neurotransmitter from the synapse.

Psychoactive substances have the ability to disrupt brain function, by altering either the release or, more often, the "reuptake" of neurotransmitters. The brain of an addicted individual can therefore no longer manage regulation.
The stimuli of pleasure and need are increasingly strong: there is much more reinforcement of pleasure and much less value in punishment.

In the case of non-produced addictions, such as gambling, work, sex, sport, compulsive shopping, etc., it is the brain's own secretions that produce its own addiction to the activity in question.