A Pain in the Neuron

What am I looking at?

This is an image of a group of pain receptor neurons that was grown in culture from stem cells. The green marks the cell bodies and projections of the neurons (1). The blue represents the nucleus of each individual neuron (2). The red/pink is a marker of neuronal activity, showing which neurons were active when this image was created (3).

Biology in the background

There is a specialized subset of sensory neurons called nociceptors that are able to sense pain. These neurons are spread throughout our skin, our muscles, and in most of our internal organs. Different types of nociceptors can sense different types of pain, including mechanical stimuli (force or pressure), chemical stimuli, and temperature.

In fact, some neurons can sense two different types of noxious stimuli, such as those that sense heat. The heat-sensing receptor, TrpV1, that’s expressed by such neurons also binds capsaicin, the chemical that gives spicy food its zing. These two sensations are similar enough that we often describe a spicy dish as “hot.”

In humans, pain-detecting cells can vary in size but their cell bodies can be as large as 12 micrometers across, or roughly six times smaller than the width of a human hair.

Technique  

This image was created using fluorescence microscopy.