3. What can drugs tell us about how neurons operate?

Students should outline how drugs target receptors on the surface of neurons and serve as agonists or antagonists to the natural neurochemicals, including details of how some block reuptake of a neurochemical, while others mimic the actions of an endogenous equivalent of the drug (e.g. cannabis). They should explain how drugs alter the activity of neurons and the effect this has on cognition, mood and behaviour, giving relevant examples. Crucially they should explain how this helps us to understand the natural role of neurotransmitters in governing these functions, citing appropriate work.

Drugs have a significant affect on neurotransmitters. There are two types of molecules that play a role in neurons, which are agonist and antagonist molecules.

Agonist molecules are similar in nature to a neurotransmitter and bind to the receptor of the neurotransmitter and mimic its effects on the body.

For instance, our body produces a marijuana-like substance, which is called anandamide and contains cannabinoid receptors. Anandamide is the substance marijuana mimics when it enters the neuron.

When marijuana is taken by an individual, the individual usually feels blissful and experiences feelings of hunger. This is because it mimics anandamide, which
has an effect on a person to make them feel blissful due to the CB1 receptor mediating the reward effects as well as contribute to appetite and feelings of pleasure.

Both dopamine and serotonin are present in the process of reward, making a person feel more emotionally elevated. Therefore, marijuana is believed to act by increasing mesolimbic dopamine and changing serotonin transmission in the neuron.

Another type of molecule is called an antagonist molecule, which blocks the neuron receptor by binding to it. An antagonist molecule, which is as found in cocaine, blocks the neuron from the ability to reuptake dopamine, which in turn puts the user into an euphoric mood until the dopamine is naturally broken down in the synaptic gap by neurotransmitters and cocaine dissolves to allow neurons to work properly again