Age Related Decrease in the Density of Dopamine D1 and D2 Receptors in Corpus Striatum of Rats

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Abstract
The densities (Bmax) and apparent dissociation constants (Kd) of D1 and D2 receptors in striatum and of 5‐HT2 receptors in cortex of rats aged 1, 3, 7 and 12 months have been determined using 3H‐SCH 23390, 3H‐spiperone and 3H‐ketanserin, respectively, as ligands. No changes in Kd's were seen. The density of D1 receptors decreases continuously from 1 month, attaining approximately 65% at 12 months of age. The density of D2 receptors increases slightly from 1 to 3 months, followed by a decrease until 12 months of age, where the level is approximately 80% of the 1 month value. The rise D2 receptor density is less apparent when calculated on a protein basis due to a concomitant increase in protein content of corpus striatum. The ratio between D1 and D2 receptors remains constant, approximately 4.2, from 1 to 12 months of age. The density of 5‐HT2 receptors decreased from 1 to 7 months and remained at this level also after 12 months.