A profound influence of steroidal (and possibly growth) hormone change during aging on the P-450 functions has been found in male rats. Direct and rapid autonomic nervous controls on glycogen metabolism in the liver is also greatly affected by aging. However, neither the responses of isolated rat hepatocyte preparations to adrenergic agonists nor the bindings of hepatocyte surface membrane preparations to adrenergic ligands was found to change with age, suggesting that the age effect on autonomic nervous control may be of central (presumably hypothalamic) origin. The present methodology of evaluating the receptor functions using Scatchard plot analysis does not seem sufficient to explore the functional alterations of receptor systems during aging and a need for new approaches that can determine certain physicochemical alterations of receptor, namely the measurement of the lateral mobility of membrane proteins during aging, is proposed.