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.