Unique in the hippocampus:Serotonin receptor plays important role in learning

Chemical messenger 5-HT4 is a marker for neurological diseases

The serotonin receptor 5-HT4 is pivotal when we learn and memorise. In a review article for the journal Neurobiology of Learning and Memory two neuroscientists of the Ruhr University Bochum (RUB) report on a receptor that plays a unique role in our brain.

Docking station for serotonin

When information is processed in the brain, synapses interact with the help of chemical messengers, the neurotransmitters. Serotonin is a neurotransmitter that is heavily involved in this process. The messenger regulates our sleeping pattern and is part of many cognitive processes. Prof. Dr. Denise Manahan-Vaughan, head of the Department of Neurophysiology at the RUB Faculty of Medicine, and neuroscientist Dr. Hardy Hagena investigated a particular serotonin receptor, a synaptic docking station for the chemical messenger. The neuroreceptor 5-HT4 plays a singular role in learning and memory processes and is a marker for certain cognitive diseases.

Important role in Alzheimer’s and depression

In their review article, the scientists report that 5-HT4 is down-regulated in illnesses that reduce cognitive capacities. On the other hand, when the receptor is activated, symptoms of depression or cognitive decline, which accompanies Alzheimer’s disease, can be reduced. The activation of the receptor launches a domino-effect, which also reduces protein deposits in the brain. These so-called “senile plaques” occur frequently in Alzheimer patients.

5-HT4 supports cognitive capacities

Furthermore, many studies have shown that 5-HT4 plays an important role in learning mechanisms – especially those that are regulated by the hippocampus. In areas as diverse as scent memory, object recognition, and navigation neuroscientists have found: the activation of the receptor supports cognitive processes.

Receptor regulates synaptic plasticity

Investigations on a cellular level performed in the lab of Prof. Dr. Manahan-Vaughan have revealed that 5-HT4 also regulates synaptic plasticity. The receptor influences how the strength of connection between synapses develops over time. It favours the so-called long-term potentiation (LTP), which describes the long-term strengthening of synaptic connections. Conversely, the receptor supresses the weakening of these contacts. It is possible that by doing this 5-HT4 also influences the content of our memories and their longevity in our minds – a unique ability among the neuroreceptors that shape learning and memory in the hippocampus. Hannah Twarkowski, PhD student at the International Graduate School of Neuroscience, recently reported on this in a joint publication with Prof. Dr. Manahan-Vaughan for the journal Hippocampus (2016, 26:875-891).