How do drugs work in the brain?

Drugs affect the brain by tapping into its communication system and meddling with the way neurons normally process information. Drugs such as marijuana and heroin can activate neurons because their chemical structure is similar to that of a natural neurotransmitter hence fooling the receptors and allowing the drugs to attach onto the receptor and activate the neurons. Even though these drugs mimic the brain’s own chemicals, they don’t activate neurons in the same way as a natural neurotransmitter.This leads to abnormal messages being transmitted through the network. Other drugs, such as amphetamine or cocaine, can cause the neurons to release abnormally large amounts of natural neurotransmitters or prevent the normal recycling of these brain chemicals. This disruption produces a greatly amplified message, ultimately disrupting communication channels.

How do drugs work in the brain to produce pleasure?

Most drugs of abuse directly or indirectly target the brain’s reward system by increasing the release of dopamine. When activated at normal levels, this system rewards our natural behaviours such as eating and sex. Overstimulating the system with drugs, however, produces euphoric effects, which strongly reinforce the behaviours of drug use—teaching the user to repeat it.

How does stimulation of the brain’s pleasure circuit teach us to keep taking drugs?

The human brain is made to remember and repeat activities that are linked to pleasure and reward. When a person feels pleasured or rewarded by an activity, the brain tells us that that activity needs to be remembered, and reminds us to unconsciously repeat it. Drugs of abuse makes use of the same mechanism, hence it teaches humans to continue taking drugs.

How does long-term drug taking affect brain circuits?

It is known that the development of drug tolerance can ultimately cause serious or permanent modification in neurons and brain circuits, which in turn harm the health of the brain. Prolonged period of drug abuse can cause changes in habits or unconscious memory systems. This change can be a long term effect, and may still affect an ex-drug addict/abuser who has been “clean” for many years.

For example, glutamate is a neurotransmitter that control the brain’s reward system and the competence to gain new knowledge. Abusing drug would revise the concentration of glutamate from its optimal concentration and the brain would then try to make up for this difference, leading to deterioration in psychological activity. One example of this form of learning is conditioning, where cues in a person’s day-to-day habitual activity or surroundings become related with the drug occurrence which can cause rampant desires whenever the person is exposed to these cues even in the absence of the drug itself.