UNIVERSITY OF MIAMI-NIH NATIONAL RESOURCE FOR APLYSIA

VOLUME 4 - FALL 1998- Page 4

RESEARCH FOCUS

VARIATIONS IN SEROTONIN AND DOPAMINE SYSTEMS IN APLYSIA CALIFORNICA

...From Page 3

We have recently examined dopamine receptor subtypes as a function of age. Our data show that the changes in the overall rate of increase can be explained by the rate of change of individual subtypes; these have maximum values at different ages. Dopamine has received less attention than serotonin in A. californica, yet there are high levels of this neurotransmitter. For example, for animals younger than five months there is more dopamine than serotonin, since the values rise faster with age than do those of serotonin. We are currently exploring dopamineís role in behavior and find that the Dl-like and D2-like receptors play a very different role.

We also find that by changing the tank conditions one changes dopamine values more than the serotonin values. Although the amounts of both dopamine and serotonin are affected by factors such as whether or not there is a protein skimmer on the tank, and the level of crowding, the dopamine values are more affected. Because the neurotransmitter values depend upon both age and tank conditions, controlling the age of the animals is a significant advantage in investigating environmental effects.

In our earlier studies we demonstrated that significant age dependent alterations in 5-HT, DA and their receptors do occur in A. californica. Both neurotransmitter and receptor levels increase with age in young animals, and thereafter the neurotransmitter levels decline, whereas the receptor levels increase gradually and finally plateau. These studies suggest that age is an important parameter that should be taken into account in studies of A. californica. Our current research is directed toward developing a greater understanding of the dopaminergic system in A. californica. Using biochemical, immunohistochemical and molecular approaches we are investigating the differential expression, distribution and localization of various DA receptor subtypes within the ganglia at different ages. We are also interested in determining the physiological significance of these changes and their responses to environmental stress.



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