Antidepressants
Antidepressants are a type of medicine typically used to treat clinical depression, as well as other conditions such as Obsessive Compulsive Disorder. Commonly, antidepressants are understood to be as simple as “increasing serotonin levels” but in reality, the processes antidepressants aid are much more complex.
Mainly, antidepressants work with monoamine neurotransmitters, containing one amino group connected to an aromatic ring by a two-carbon chain. There are many different types of monoamines including dopamine, serotonin and noradrenaline - all of which control mood. However, the most effective and common antidepressants seem to act on one type of neurotransmitter - serotonin, that is also linked to digestion, blood clotting and bone density.
To understand how these antidepressants work, the functioning of serotonin needs to be clarified. For a message to be passed from one nerve to another, at the end of the first nerve the message must be converted into a chemical signal- this is what serotonin does. The space between the two nerves is called a synapse and once serotonin is in the synapse, it can be taken up by the receptors in the postsynaptic cell. The serotonin cannot stay in the synapse for too long hence the nerve cell sending the message takes back the serotonin, storing it. This recycling of serotonin (or any neurotransmitter) is called reuptake.
When enough serotonin is not produced by nerve cells of the brain there are insufficient serotonin molecules to absorb by the postsynaptic cell and messages are not carried through. This is where SSRIs (Selective serotonin reuptake inhibitors) come in. They stop serotonin from being reabsorbed in the presynaptic cell, allowing it to stay in the synapses for the message to be carried through.
Antipsychotics
Antipsychotics are a type of psychiatric medication which are available on prescription to treat psychosis including diseases such as schizophrenia. The cause of psychosis is an increase in one of the monoamines mentioned earlier - dopamine.
Normally, dopamines are involved in enhancing the organism’s learning about rewards and their associations, and driving goal-directed behaviour. However extremely high levels of it create delusions in psychosis.
There are four main types of dopamine receptors that allow neurotransmission- D1, D2, D3, D4. Antipsychotic drugs specifically target D2 receptors that are present not only on the postsynaptic membrane, but on the cell bodies, dendrites and nerve terminals of presynaptic cells as well, antipsychotic compounds can interfere with dopaminergic neurotransmission at various sites in both the pre- and postsynaptic cell. Therefore, by targeting dopamine receptors, antipsychotic drugs reduce extremely high levels of dopamine which are harmful and bring them back to their normal function of recognising rewards and learning.
Bibliography
Comentários