Dopamine receptor subtype density as a function of age in Aplysia californica

The age-associated changes in dopamine subtype receptors were examined in A plysia californica. The density of the subtype receptors D1, D2, D3 and D4 was examined in the ganglia from 4.5-, 6-, 8-, 9- and 12-month animals. Rec eptor analysis was performed by examining the binding of radiolabeled ligan ds to the individual subtypes. [H-3]SCH23390 and [H-3]Clozapine were used t o analyze D1 and D4 specific binding. [H-3]Quinpirole was used for determin ing D2 and D3 specific binding. Specific binding was found to be present fo r all four receptor subtypes. All receptor subtypes showed an increase in d ensity from 4.5 to 6 months. From 6 to 8 months D2 and D3 decreased, while DI and D4 increased. D4 showed the strongest increase. All four subtypes ex amined showed decreases from 8 to 12 months. ANOVA results indicated age wa s a significant factor in the subtype receptor density for all receptor typ es. (C) 2001 Elsevier Science Inc. All rights reserved.