Specks of Serotonin

What am I looking at?

This image is a 1.5-millimeter-thick horizontal slice through the brain of a mouse. It shows the neurons that produce serotonin in purple (1) and pyramidal neurons in green (2).

Biology in the background

Serotonin is a biochemical compound that contributes to many important biological functions, but it’s best known for its role in influencing mood. In fact, the most widely used antidepressants are a class of drug called selective serotonin reuptake inhibitors (SSRIs). These drugs keep serotonin in the brain’s synapses longer by blocking its reuptake back into the neuron that released it; more time in a synapse means more ability to act on its targets, increasing serotonin signaling. An increase in serotonin signaling in certain areas of the brain has been shown to decrease negative emotions, such as those associated with depression and anxiety.

Pyramidal neurons are one of the most common types of neurons in the brain and are so named because of their pyramid-shaped cell bodies. These neurons are involved in a wide range of cognitive functions, including memory, movement, the processing of sensory information, and much more.

Many pyramidal neurons have serotonin receptors and may therefore be involved in controlling mood and emotions.

Serotonergic neurons vary in size but on average have cell bodies that are about 38 microns across, or roughly half the width of a human hair. Pyramidal neurons also vary in size but on average have cell bodies that are about 20 micrometers across, or roughly 3.5 times smaller than the width of a human hair.

Technique

These images were created using confocal microscopy.