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A drug can be defined as any substance able to produce a change to our body. Drugs able to produce a known effect on the nervous system are referred to as psychoactive drugs, for their ability to influence cognitive and behavioral abilities regulated by the brain’s interconnected network of neurons and to overcome the blood–brain barrier (BBB).

The BBB has been only quickly covered in this lesson, but it is a very interesting topic that you can learn more about here and here. Did you know that it is not the only “barrier” in our body system? Check this out to find out more.

The main known influence of psychoactive drugs is at the neuronal level. A neuron is a specific kind of cell, composed by a body (or soma), some dendrites and an axon. Synapses are placed along the dendrites or the axon, where they get in contact with the dendrite or the axon of another neuron. A synapse is not a physical contact between the two parts, but rather a space where the two parts are very close to each other, so close that the neurotransmitters (such as, dopamine, serotonin, noradrenaline, acetylcholine or GABA), can be exchanged between the sending (pre-synaptic) and receiving (post-synaptic) neuron. The sending neuron has a terminal button where its neurotransmitters are stored, ready to be released. The receiving neuron is equipped with receptors, structures able to bind with specific neurotransmitters. Interested in finding out more about how nerves work? Watch this TED-Ed Lesson.

Each neurotransmitter plays a different main role in the regulation of our behavior, emotion and cognition. Dopamine regulates movements, energy and our perception of reward, punishment and feelings of pleasure. Serotonin mainly modulates mood and impulsivity. Noradrenaline regulates mainly energy, arousal, alertness and pleasure. Acetylcholine controls movement, memory, motivation and sleep. GABA is primarily involved in arousal, judgment and impulsiveness. And there are many more. Learn more about neurotransmitters here.

The signal exchanged between neurons is referred to as an electrochemical signal. Why is that? A neurotransmitter is a chemical messenger. When it binds to the receptor, it generates a small amount of electrical activity on the receiving neuron. This electrical activity then spreads thought the rest of the neuron. If the amount of electricity on a given neuron is strong enough, then that signal is passed on to other neurons by releasing a new neurotransmitter. A receiving neuron becomes a sending neuron.

Some medical and research methods (DBS, tDCS, TMS) point to new ways to alter the communication between neurons. Rather than directly altering the exchange of neurotransmitters (the chemical message), brain stimulation techniques can be used to alter the electro-magnetic state of neurons, thus influencing their communication.

Drug use has short and long term consequences on the brain’s functioning. Health agencies, supported by scientific evidences, pointed out how the abuse of recreational as well as prescription drugs can have serious consequences on health.