Decrease of muscarinic M2 cholinoceptor gene expression in the heart of aged rat

It is well known that the baroreflex activity decreases with aging. However , the mechanisms of this change are still not clear. Thus, we investigated one of the parameters to see whether aging alters gene expression of muscar inic receptors in the heart of Wistar rat aged between 2 months (adult) and 24 months (aged). The mRNA level determination by Northern blot analysis f or muscarinic M2 cholinoceptors in aged rat was decreased as com pared to t hat in 2-month-old rats. Quantification of receptor protein using selective antibodies indicated that the level of muscarinic M2 cholinoceptor in the heart of 24-month-old rats was lower than that in 2-month-old animals. Thes e results indicate the decrease of muscarinic M2 cholinoceptor in heart wit h aging that may contribute as one of the parameters for dysfunction in bar oreflex activity. (C) 2001 Elsevier Science Ireland Ltd. All rights reserve d.