Scientists have found a reason why some people never seem to get warm while others never seem to feel the cold: some nerve cell receptors deep in the body are stimulated by signals other than temperature.
These cells never come in contact with environmental signals like those near the skin but are studded with receptors that appear to get sensory input from hormones, proteins and other biochemical compounds within the body.
The findings, published in 2004 in the Journal of Neuroscience by researchers at the University of Florida, advance the understanding of why menopause, depression and fevers sometimes cause chills along with feeling overheated.
‘What we are working to understand is the physiological and pathological roles of these receptors and why some people may feel cold or pain despite external stimuli,’ said neuroscientist Jianguo Gu, a researcher in the university’s College of Dentistry and the McKnight Brain Center.
‘That could explain why it is that you and I can sit in the same space and you will feel comfortable and I may feel cold, yet the environmental stimuli are the same.’
Other scientists have only recently identified hot and cold nerve cell receptors in the peripheral nervous system located just beneath the skin. This is the system that tells the brain to pull the hand back from the flame or to bundle up when it’s cold outside.
But what Gu and his colleagues found is that there are receptors so deep in the body that they literally chill to the backbone. ‘In addition to under the skin on the peripheral side of the nervous system, there are also cold receptors on the central side of the peripheral nervous system within the spinal cord,’ he said.
The researchers studied the effects cool temperatures and menthol, a chemical derivative of peppermint associated with cooling effects, had on a specific sensory molecule found on the tips of peripheral nerves.
They placed central and peripheral nerve cells taken from rats together in lab dishes to mimic the cells’ relationship to each other inside the body. Then they exposed the cells to cold and menthol.
