Bitter on the Brain

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By Nicole Garneau, PhD

Monday mornings I sort through the weekend's long trail of emails. As part of this routine, I receive my weekly search results on "chemoreception" from an online database of biomedical publications. Usually I scan the titles and chalk it up to a "read later" file in my head- not today.

Today, there was one title that really caught my eye, "Functional Bitter Taste Receptors are Expressed in Brain Cells." I clicked on the link to read the abstract, crossing my fingers that I had access to the full paper (sometimes publishers don't allow open access for up to a year after publication).

It turns out, it's not the newest of news, as the study was published in March, but it's new to me because my search filter only pulled it up today, a good 2 months late for some reason. I read on with interest and found that the study was done in rats, and the scientists show evidence that yes in fact, at least in rats, the animals have bitter receptors that in their brains that when they bind bitter chemicals, it activates the cell.

What's interesting will be to see if there are taste cells in the brain that are similar to taste cells in the tongue (within taste buds, shown on the left) and to the taste cells that have been found in the digestive system (shown on the right). Both of these cell types are shown below with the signalling pathways that occur once the cell is activated by a taste molecule. (This image is from a paper published by David E. Cummings and Joost Overduin in 2007.)

taste cells 

I don't have access to the full paper "Functional Bitter Taste Receptors are Expressed in Brain Cells", but the authors indicate that they discuss the physiological relevance of this in their results section. I don't know much about the anatomy of rats, so I can't guess what the authors discuss, but it is important to note that although mice and rats are studied to understand mammalian biology, and although there are many genes that are similar between these groups, results in one species does not necessarily mean you will find the same results in another species. This point that was made clear in the recent AChemS (Association for Chemoreception Sciences) meeting I attended in April, where even distinct differences between mice and rats in terms of taste and smell were discussed. So it is unclear at this point if mice or even humans also have bitter receptors in their brains.

I want to also note that these authors were not at AChemS, and so I don't have any insight from the meeting on the general feel for this new discovery among other taste and smell scientists. I did a quick to search on Bing to see if the story had been picke dup elsewhere, but I couldn't find any other information. If I learn more from my colleagues at the Rocky Mountain Taste and Smell Center, I will put it up on the blog as a follow up post.

Until then, for those of you who are interested, you can read the abstract HERE

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