Decreased expression of 5-HT1A in the circumvallate taste cells in an animal model of depression.

OBJECTIVE:It has been reported that stress can cause anhedonia, a core symptom of depression, and also affect taste responses of the stressed subjects. Anhedonia refers to a reduction of the ability to experience pleasure, which can be detected by decreased response to palatable food in rats. The present study was conducted to examine if stress-induced anhedonia is accompanied by changes in gene expression for taste. DESIGN:For anhedonia test, rats had free choices of cookies, a palatable food, and chow for 1h following 1h of daily restraint sessions. To examine the development of behavioral depression by restraint stress, ambulatory activity and forced swim tests were performed. Taste cells were harvested from the circumvallate papillae of rats on the 1st, 3rd and 7th day of stress exposure and subjected to the analysis of gene expression for taste. RESULTS:One hour of daily stress exposure did not affect chow intake during the entire experimental period. However, from day 2 cookie intake was suppressed, suggesting the development of anhedonia. Ambulatory activity was significantly decreased, and immobility during forced swim test was increased, after the 7th day of stress exposure, but not before. 5-HT1A mRNA expression, but not T1R2, T1R3, T2R6, α-gustducin or PLCβ2 mRNA expression, appeared to be decreased after the 3rd day of stress exposure. CONCLUSION:Reduced expression of 5-HT1A in the taste cells, possibly leading to a reduced processing of taste information for palatable food, may additively contribute to the development of anhedonia as a pre-symptomatic feature of depression in stressed subjects.