The effect of age on muscarinic receptor transcripts in rat brain

The expression of five muscarinic receptor mRNAs (m1, m2, m3, m4, m5) was examined in neostriatum, hippocampus and frontal cortex of 3, 18, and 33 month old rats. Transcripts for ml (3.0 kb), m2 (6.2 kb), m3 (4.5 kb) and m4 (3.3 kb) were detected in all brain regions studied. A 6.0 kb transcript for the m5 muscarinic receptor was observed in hippocampus and neostriatum, but was not detected in frontal cortex. Age-related changes in muscarinic receptor transcript expression were restricted to the neostriatum, where m3 and m4 mRNAs were decreased at both 18 and 33 months of age. The reduction in transcripts of m3 and m4 receptors may contribute to changes in cholinergic system function with age.