Abstract
Familiarity discrimination has a significant impact on the pattern of food intake across species. However, the mechanism by which the recognition memory controls feeding is unclear. Here, we show that the nematode Caenorhabditis elegans forms a memory of particular foods after experience and displays behavioral plasticity, increasing the feeding response when they subsequently recognize the familiar food. We found that recognition of familiar food activates the pair of ADF chemosensory neurons, which subsequently increase serotonin release. The released serotonin activates the feeding response mainly by acting humorally and directly activates SER-7, a type 7 serotonin receptor, in MC motor neurons in the feeding organ. Our data suggest that worms sense the taste and/or smell of novel bacteria, which overrides the stimulatory effect of familiar bacteria on feeding by suppressing the activity of ADF or its upstream neurons. Our study provides insight into the mechanism by which familiarity discrimination alters behavior.DOI:http://dx.doi.org/10.7554/eLife.00329.001.
Highlights
Wholesome food is essential for survival and animals have developed nervous systems that guide food intake
To test if familiarity discrimination alters feeding in C. elegans, we tested if exposure to a particular bacterium alters its subsequent consumption
We found that the Neuroscience feeding rates of the animals on familiar bacteria were significantly higher than the rates on novel bacteria, regardless of bacterial type (Figure 1B,C)
Summary
Wholesome food is essential for survival and animals have developed nervous systems that guide food intake. In response to previously encountered stimuli, this ability allows knowledge gained from prior experience to guide animals to respond with an altered output that is beneficial for their survival. Familiarity discrimination is mere sensation of prior occurrence and does not accompany episodic memory (Brown and Aggleton, 2001). Some species including humans consume familiar food more actively than novel food (Diaz-Cenzano and Chotro, 2010), probably to avoid possible pathogens. Other species consume familiar food less actively than novel food (Wang and Provenza, 1996), probably to assure balanced nutrition
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