Serotonin VS Dopamine

Overview

Serotonin and dopamine are both neurotransmitters, which are chemical messengers that allow nerves to communicate with each other. They act in similar parts of the body but vary in effect.

Understanding serotonin

Serotonin is known chemically as 5-hydroxytryptamine (5-HT). This neurotransmitter affects not only your mood but also your digestive and immune system.^1,2 Serotonin can also have a role in memory, attention, reward, anger, and sleep cycles.

Serotonin in the brain is produced in a part of the brainstem called the Raphe Nuclei. Serotonergic fibres are then produced and projected to the nucleus accumbens, which is an area of the brain responsible for reward pathways.

After reaching the nucleus accumbens, serotonin is then projected through multiple regions of the brain, including the cerebellum, hippocampus, and spinal cord.

Neurotransmitters fall into different categories based on the way they interact with receptors. Serotonin is an inhibitory neurotransmitter, meaning it makes it harder and less likely for a neuron to continue to fire. Serotonin, therefore, provides balance to the excitatory effects of other neurotransmitters.

The way serotonin is transmitted between neurons is referred to as neurotransmission. Serotonin is released into the synaptic cleft, a gap between neurons. Once in this gap, serotonin will then do one of 3 things: bind to the serotonin receptor in the other neuron, be digested by an enzyme called monoamine oxidase, or be reabsorbed back into the releasing neuron.

Understanding dopamine

Dopamine is made in the base of your brain through a two-step process. An amino acid called tyrosine is first made into another amino acid called L-dopa, which is then made into dopamine. 

Dopamine is responsible for feelings of pleasure after participating in activities that activate the reward system in your brain. It also helps you concentrate and learn new information.

Dopamine also plays a role in muscle movement, heart rate, lactation, pain, sleep, and function of your kidney and blood vessels. Dopamine is classed as both an inhibitory and excitatory neuron and therefore has a variety of effects. 

Dopamine is made in many regions of the brain, including the hypothalamus and olfactory bulb. However, it is most concentrated in the substantia nigra and the ventral tegmental area located in the midbrain. When you are exposed to certain rewarding activities, this stimulates the increase in dopamine production from the ventral tegmental area (VTA). Dopamine is then transported through different pathways. The two main ones are called the “mesolimbic” and the “mesocorticol” pathways. 

In the transportations through the mesolimbic pathway, dopamine is activated in the VTA and then projected to the nucleus accumbens, an area that is important in the brain's reward circuit. Dopamine levels then rise in the nucleus accumbens and project to the limbic system, including the amygdala and hippocampus. Connecting to the amygdala contributes to feelings associated with rewards. Connecting to the hippocampus can help to link memory and learning to the reward. In the transportation through the mesocortical pathway, dopamine gets activated by the VTA. However, they then project to the cerebral cortex and frontal lobes. The frontal lobes are linked with the conscious experience of pleasure and reward; this can link attention and motivation to the rewarding experience. During neurotransmission, dopamine is released into the synaptic cleft.³

Difference between serotonin and dopamine

• Dopamine relays signals between neurons that control body movements and coordination.
• Dopamine plays a role in the brain's pleasure and reward centres. 
• Serotonin helps regulate digestive function, appetite, metabolism, and gut mobility.
• Serotonin suppresses while dopamine stimulates hunger.
• Serotonin inhibits impulsive behaviour while dopamine enhances impulsivity.

Similarities between serotonin and dopamine

• Both are monoamine neurotransmitters. 
• Both have an influence on people's moods and emotions.
• Both act in the brain and body. 
• They are neuromodulators, meaning they can communicate with many other neurons that are far away from their respective release sites. 
• They also send signals that last longer than signals of other neurotransmitters.

Conditions or illnesses connected to serotonin and dopamine

Having abnormal levels or imbalances of these two neurotransmitters can affect mood disorders and result in distinct conditions.^4,5,6 These include:

• Depression
• Anxiety
• Schizophrenia
• Digestive disorders
• Sleep disorders
• Parkinson's disease

FAQs

Can serotonin and dopamine cause depression?

These two neurotransmitters play an important role in mood regulation but do not directly cause depression. Depression is usually caused by environmental factors, such as stress and trauma in a person's life. There are also genetic factors that may determine the susceptibility to developing depression. 

Due to the areas of the brain they reside in and affect, having an imbalance of these neurotransmitters can be linked to certain symptoms of depression. For example, an imbalance of dopamine may lead to low motivation or feelings of hopelessness, while a serotonin imbalance can affect the processing of emotions.

Can serotonin and dopamine cause anxiety?

Low serotonin has been linked to anxiety; however, the cause of anxiety is likely due to environmental factors, genetics, and family history. 

What can serotonin and dopamine do to mental health

Correcting imbalances in serotonin and dopamine is thought to be beneficial for people with mood disorders, as they play a vital role in many different areas of the brain related to mood and decision-making.

What will happen if serotonin and dopamine are too high or too low

Having too high a level of serotonin can cause a life-threatening medical condition called serotonin syndrome or serotonin toxicity. This is caused by taking too much serotonergic medication at the same time, and these include 

• Selective Serotonin Reuptake Inhibitors 
• Serotonin Noradrenaline Reuptake Inhibitors
• Tricyclic antidepressants 
• Certain migraine medications which end with the word triptan

Opioid pain relievers can also interact with these medications to increase the levels of serotonin.

Having too low a level of serotonin can affect gut motility, digestion, and, in some instances, lead to having high levels of dopamine, as serotonin can inhibit dopamine production.

High levels of dopamine can cause feelings of euphoria, which can be caused by both legal and illegal substances such as nicotine and cocaine. This can create a potential for addiction, which could then create problems such as depression when withdrawing from these things.

High levels of dopamine have also been linked with hallucinations and delusions, which can be symptoms of schizophrenia. 

Summary

In conclusion, serotonin and dopamine are two incredibly important neurotransmitters for both brain and bodily function, but differ in their effects. Serotonin helps regulate mood, body temperature, appetite, and gut motility. Dopamine regulates mood, particularly in the brain's pleasure and reward systems, and muscle movement.