HOW DRUGS AFFECT NEUROTRANSMITTERS

How do drugs make us feel so euphoric? And at the same time, how can mere molecules cause behaviours so alienating as those that accompany dependency?

Human behaviours and emotions are modulated by neurotransmitters that act as keys between neurons. The amount of any given neurotransmitter in the brain’s circuits is precisely controlled by numerous feedback mechanisms, somewhat the same way that a thermostat keeps a room around a certain temperature.

Drugs are substances that disturb this delicate balance, because they have “passkeys” that let them open certain “locks” located between the neurons. The brain automatically adjusts to these substances from outside the body by producing fewer of its own natural “keys”. It thereby achieves a new state of equilibrium that is maintained until the body starts to miss the external substance. At that point, the person experiences a craving that will persist until the neurons that went on vacation get back to work.

Among the brain circuits most affected by drugs is the one associated with pleasure. This reward circuit that is overstimulated by drugs uses a particular neurotransmitter called dopamine. So researchers have not been surprised to discover that practically all of the drugs that cause dependencies increase the amount of dopamine in the reward circuit.

They do so in different ways. Drugs act by imitating, stimulating, or blocking the effects of certain neurotransmitters.