Relationship between the grades of a learned aversive-feeding response and the dopamine contents in Lymnaea.
The pond snail Lymnaea learns conditioned taste aversion (CTA) and remembers not to respond to food substances that initially cause a feeding response. The possible relationship between how well snails learn to follow taste-aversion training and brain dopamine contents is not known. We examined this relationship and found the following: first, snails in the act of eating just before the commencement of CTA training were poor learners and had the highest dopamine contents in the brain; second, snails which had an ad libitum access to food, but were not eating just before training, were average learners and had lower dopamine contents; third, snails food-deprived for one day before training were the best learners and had significantly lower contents of dopamine compared to the previous two cohorts. There was a negative correlation between the CTA grades and the brain dopamine contents in these three cohorts. Fourth, snails food-deprived for five days before training were poor learners and had higher dopamine contents. Thus, severe hunger increased the dopamine content in the brain. Because dopamine functions as a reward transmitter, CTA in the severely deprived snails (i.e. the fourth cohort) was thought to be mitigated by a high dopamine content.
Research Center of Mathematics for Social Creativity, Research Institute for Electronic Science, Hokkaido University, Sapporo 060-0811, Japan.|CREST, Japan Science and Technology Agency, Kawaguchi 332-0012, Japan.
Hitoshi
H
Aonuma
Laboratory of Functional Biology, Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, Sanuki 769-2193, Japan.
Mugiho
M
Kaneda
Laboratory of Functional Biology, Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, Sanuki 769-2193, Japan.
Dai
D
Hatakeyama
Research Center of Mathematics for Social Creativity, Research Institute for Electronic Science, Hokkaido University, Sapporo 060-0811, Japan.
Takayuki
T
Watanabe
Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada T2N 1N4.
Ken
K
Lukowiak
Laboratory of Functional Biology, Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, Sanuki 769-2193, Japan eito@waseda.jp.|Department of Biology, Waseda University, Shinjuku, Tokyo 162-8480, Japan.
Etsuro
http://orcid.org/0000-0002-1877-6566
E
Ito
Conditioned taste aversion; Dopamine; Food deprivation; Long-term memory; Lymnaea