Taste perceptions

Taste sensitivity is altered by changing levels of so-called
neurotransmitters that are thought to be involved in depression, British investigators report. In a press release from the University of Bristol, Dr. Lucy F. Donaldson said, “we hope that using a taste test in depressed people will tell us which neurotransmitter is affected in their illness,” and thus assist in treatment decisions. Neurotransmitters are chemicals that generate nerve signals in the brain. Serotonin, dopamine and noradrenaline are three that are believed to affect mood states. Some reports have linked changes in taste sensitivities with severe depression and anxiety.

Donaldson and her associates explored taste changes among 20 healthy adults, before and after they were given the antidepressant Paxil, which raises the amount of serotonin available, and Edronax, which does the same for noradrenaline. The subjects’ taste responses were determined by applying varying concentrations of “tastants” to the tip of the tongue using a cotton swab. After 5 seconds, subjects reported if they could taste the stimulus at that concentration. They rinsed their mouths with water between each solution. The tests were repeated 2 hours after the subjects took the test drugs.

The results, reported in the Journal of Neuroscience, showed that Paxil increased sensitivity to sweet and bitter tastes. Conversely, Edronax lowered taste thresholds to bitter and sour tastes. None of the subjects exhibited signs of depression, although some had higher anxiety scores. In the most anxious participants, taste sensations appeared to be blunted, with significantly higher recognition thresholds for bitter and salt taste. “These results support an important and basic role for serotonin and noradrenaline in taste function and may explain why anxious and depressed individuals exhibit diminished appetite,” the researchers add.

SOURCE: Journal of Neuroscience, December 6, 2006.