Thymus-induced recovery of age-related decrease of brain cortex αand βadrenoceptors

It has previously been demonstrated that thymus exerts a regulatory influence on βadrenergic system during aging. In particular, it has been shown that thymus can correct the βadrenoceptor density decrease in old mice. In the present paper results of experiments are reported dealing with the influence of the thymus on αadrenoceptors of mouse brain cortex. Both subtypes of αadrenoceptors are studied separately, using different labelled ligands. Results show that αI-adrenoceptor density decreases in old animals, while α2-adrenoceptor density does not change significantly. A neonatal thymus grafted into old recipients is capable of correcting the alteration observed in old mice. The differential impairment of αadrenoceptors resembles that one previously observed on βadrenoceptors, where β1-type decreases in number during aging with a parallel decrease of adenylyl-cyclase activity, while β2-type remains unchanged.