Experiential effects of appetitive and nonappetitive odors on feeding behavior in the blowfly, Phormia regina: a putative role for tyramine in appetite regulation.
In humans, appetite is affected by food experiences and food flavors. In the blowfly Phormia regina, we found that feeding threshold to sugar increased in the presence of the odor of D-limonene and decreased in the presence of the odor of dithiothreitol (DTT). Using these odors as representative nonappetitive and appetitive flavors, we demonstrated the role played by tyramine (TA) in appetite regulation by experiences of food flavors. When fed with sucrose flavored with D-limonene for 5 d after emergence, flies showed subsequent decreased appetite to plain sucrose, whereas when they were fed with sucrose flavored by DTT they showed increased appetite. However, mushroom body (MB)-ablated flies did not show these patterns. This suggests that MB, one of the primary memory centers of the insect brain, is necessary for the flies to apply previous experiences of food flavors to appetitive learning behaviors. In addition, flies' previously acquired decreased or increased appetites showed parallel changes with both octopamine (OA) and tyramine levels in the brain. However, injection experiments with OA, TA, or their agonist and antagonist indicated that TA more directly mediates feeding threshold determination, which was affected by acquired memories of food flavors.
Nisimura
Tomoyosi
T
Department of Applied Biology, Faculty of Textile Science, Kyoto Institute of Technology, Kyoto 606-8585, Japan.
Seto
Atsushi
A
Nakamura
Kyoko
K
Miyama
Mayumi
M
Nagao
Takashi
T
Tamotsu
Satoshi
S
Yamaoka
Ryohei
R
Ozaki
Mamiko
M
D000818:Animals; D001069:Appetite Regulation / Q000187:drug effects / Q000502:physiology*; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D004175:Diptera; D004305:Dose-Response Relationship, Drug; D005247:Feeding Behavior / Q000187:drug effects / Q000502:physiology*; D009812:Odorants; D013395:Sucrose / Q000008:administration & dosage; D014439:Tyramine / Q000378:metabolism*
D013395:Sucrose; D014439:Tyramine