The ratio of striatal D1 to muscarinic receptors changes in aging rats housed in an enriched environment

The enriched environment (EC) causes morphological plasticity in striatal c ells that express D1 and D2 receptors. We used radioligand binding assays t o examine whether EC produces plasticity in striatal receptor density and r eceptor density ratios. After 30 days of EC, 2-year-old rats had a higher r atio of D1 to muscarinic receptors in striatum relative to singly housed ra ts. Assays also showed trends for a greater ratio of D1 to cannabinoid rece ptors and a greater density of D1 receptors in striatum after EC. D2 recept or density was unaffected by the EC condition. (C) 2000 Elsevier Science B. V. All rights reserved.