3.1 Acetylcholine, Serotonin & PEA


Acetylcholine is a neurotransmitter that wears many hats at once. It is active in both the central and peripheral nervous systems. It is involved in movement, both voluntary and involuntary. It plays both an excitatory and inhibitory role, which basically means that it can speed up or increase responses, or slow down and decrease responses.

In the central nervous system, it plays a vital role in memory and learning and is involved in neuroplasticity – the development of new nerve connections and pathways in the brain when we learn new things. Every time we learn something new, like a skill or information about a subject, new pathways and connections between neurons take place. This change and growth is called neuroplasticity. It is an important part of arousing our senses when we wake up in the morning.

Acetylcholine is a very important part of the decision making process. This doesn’t mean sitting pondering over a subject – like ‘shall I do that skydive’, rather it’s those automatic almost unconscious decisions that we make in response to sensory stimuli. The example of touching something hot given earlier is relevant here as acetylcholine is involved in deciding that it’s a good idea to get your hand out of the way. A deficit of acetylcholine has been associated with memory loss and low mood. There is no suggestion as to whether lowered levels are a cause, just that an association has been found.


Serotonin has to be the most well-known of all neurotransmitters. It is one of the neurotransmitters that are widely talked about. Everybody has heard of it and has almost become a little bit fashionable. This may be because it is a neurotransmitter that is very widely understood and one that has become a key target in drug therapy for some of our most debilitating mental health issues. Why is this?

Serotonin is one of the main neurotransmitters involved in how we feel. It is synthesised in the body from the amino acid, tryptophan, and over 90% of it is stored in the gut! It has many roles to play in the body from controlling elements of bone metabolism to controlling localised aspects of gut function. However, the one thing that serotonin does that really overshadows everything else, is to make us feel good!

Serotonin is the feel-good chemical that keeps us happy and upbeat. It keeps our mood stable too. Serotonin also regulates our appetite, regulates sleep patterns and is involved in memory and sexual desire. A deficiency of serotonin has been linked to depression.


Phenylethylamine or PEA for short is something of a special substance, and one that has become a bit of a darling of the health world, and understandably so. PEA is a compound that is released when we fall in love. Basically, it speeds up the to and fro of information between neurons. Just the smallest amount of it can induce feelings of euphoria, bliss, infatuation and love. Whilst this is produced in the brain, it is also present in some foods, including chocolate! This may explain a lot. Low levels of PEA have been associated with depression.