CHANGES OF LYMPHOCYTE BETA-ADRENERGIC RECEPTORS AND PLATELET SEROTONIN REUPTAKE SITES IN AGING AND DEMENTIAS

We have studied the kinetic constants of beta-adrenergic receptors in lymphocytes and of serotonin uptake sites in platelets from adult and elderly volunteers and from aged patients with a diagnosis of multi-infarct dementia (MID) or senile dementia of Alzheimer's type (SDAT). The results showed that in the physiological aging process, beta-adrenergic receptor density is reduced and 5HT transport system is enhanced. MID is associated to a loss of beta-adrenoceptor affinity and a slight increase in the capacity of 5HT uptake. The kinetic constants of both beta-adrenergic receptors in lymphocytes and 5HT uptake sites in platelets from SDAT patients were comparable to those observed in the adult population, being thus different from those found in the aged matched volunteers. These changes could be interpreted as resulting from compensatory mechanisms that replaced altered plasma monoamine concentrations. The apparent absence of such changes in SDAT patients could suggest the lack of these compensatory effects.