A re-evaluation of changes in rat striatal D-2 dopamine receptors during development and aging.

High affinity binding of 3H-spiperone to D-2 dopamine receptors was measured in membrane fractions prepared from striata of male Sprague-Dawley rats aged 0.75-25 months. 3H-Spiperone bound with approximately 0.11 nM affinity in all age groups studied. The maximum number of D-2 receptors initially increased with age, peak adult levels being reached by 4 months of age. Receptor density declined by 33% over the next 7 months and no further loss of receptors was apparent between 11 and 25 months of age. Such a time-course suggests a loss of rat D-2 receptors that occurs, at least in this strain, earlier than has previously been appreciated, and appears to be in agreement with preliminary positron emission tomographic studies in living man.